ASTIS - Arctic Science and Technology Information System


A search of the ASTIS database for "TAG MAGS" has found the following 52 records, which are sorted by first author.


Comparing the performance of the Canadian Land Surface Scheme (CLASS) for two Subarctic terrain types   /   Bellisario, L.M.   Boudreau, L.D.   Verseghy, D.L.   Rouse, W.R.   Blanken, P.D.
(Atmosphere-ocean, v. 38, no. 1, Mar. 2000, p. 181-204, ill., 1 map)
References.
ASTIS record 48877.
Languages: English
Libraries: ACU

The Canadian Land Surface Scheme "CLASS" is tested for two major terrain types found in the northern Hudson bay Lowland. Soil temperature and energy balance measurements for sedge fen wetland and dwarf willow-birch forest near Churchill, Manitoba, are compared with simulations both with and without the new organic soil parametrization that has been developed for CLASS (Letts et all., 2000), for eight datasets spanning six years (1990 through 1995). With the exception of the sensible heat flux at the sedge site, the new version of CLASS with the organic soil parametrization improves the energy budget simulation at each of the research sites. Both the latent (QE) and ground (QG) heat flux were modelled well; however, some modifications were required to simulate the continued evaporation from these sites once the water table receded below the first soil layer. The sensible heat flux (GH) was the least well simulated component of the energy balance in both versions. Temperatures for the top two soil layers were consistently overestimated by the mineral soil parametrization for both terrain types, whereas the organic soil parametrization showed significant improvement. The new water table diagnostic algorithm in the organic soil version satisfactorily estimates the position of the water table, even under a large range of climatic conditions. The inclusion of organic soil parameters in CLASS, and the subsequent improved handling of soil moisture, is a significant contribution to model development, and provides a physically-based capability for simulating northern peatlands within land surface models. (Au)

A, C, E, F, H, J
Atmospheric circulation; Birches; Bogs; Climate change; Energy budgets; Environmental impacts; Evaporation; Forests; Groundwater; Mathematical models; Numeric databases; Peat; Sedges; Shrubs; Soil moisture; Soil temperature; Wetlands; Willows

G0824, G0825
Churchill region, Manitoba; Hudson Bay region, Manitoba; Hudson Bay region, Ontario; James Bay region, Ontario


Collapse of floating ice covers under vertical loads : test data vs. theory   /   Beltaos, S.
(Cold regions science and technology, v. 34, no. 3, May 2002, p. 191-207, ill.)
References.
ASTIS record 51868.
Languages: English
Web: doi:10.1016/S0165-232X(02)00004-6
Libraries: ACU

Various criteria have been advanced to describe and predict the conditions under which a load will break through a floating ice cover. As a rule, the experimental basis for each of these criteria has been limited, and a comprehensive performance evaluation has yet to be carried out. Criteria based on stress, strain, deflection and strain energy are discussed first, in conjunction with the viscoelastic nature of ice and the mode of failure of an ice sheet. Five data sets are then described and utilized to test and compare the performance of failure criteria that have been proposed in the literature. Stress-based criteria, though simple to use, are only useful for very brief loading because they do not account for loading time and history. Strain- and deflection-based criteria are also subject to time and history effects that similarly limit their applicability to short-term loads. On the other hand, strain-energy criteria are found to apply equally well to short- and long-term loads of different histories. This feature is attributed to implicit consideration of time and load-history effects through integration of the deflection-load variation. Safety implications and future research avenues are discussed. (Au)

G
Bearing capacity; Creep; Elasticity; Fracturing; Ice loads; Ice sheets; Lake ice; Mathematical models; Salinity; Sea ice; Strain; Stress; Testing; Thickness

G0815, G0822
Joseph Lake, Alberta; Resolute Bay, Nunavut


Spatial and temporal variability of Canadian monthly snow depths, 1946-1995   /   Brown, R.D.   Braaten, R.O.
(Atmosphere-ocean, v. 36, no. 1, Mar. 1998, p. 37-54, ill., maps)
References.
ASTIS record 48867.
Languages: English
Libraries: ACU

In 1995 the Atmospheric Environment Service of Canada (AES) made a major effort to digitize paper records of daily and weekly snow depth that were not in the Canadian Digital Archive of Climate Data. This resulted in the extension of the snow depth record back to the late 1940s at many stations, and the filling of missing data from a number of stations, particularly in the Arctic. This paper describes the database, the methods used both for quality control and to reconstruct missing data, and presents an analysis of the spatial and temporal characteristics of the data over the 1946-1995 period. Principal component analysis of monthly snow depths revealed that snow depths varied coherently over relatively large regions of Canada, with dominant centres of action located over the West Coast, Prairie, Yukon-Mackenzie, southern Ontario, northern Québec and Maritime regions. In many cases, nodes of coherent snow depth variations were associated with corresponding nodes of coherent snow cover duration fluctuations, with the two time series exhibiting significant positive correlations. Winter and early spring snow depths were observed to have decreased significantly over much of Canada in the 1946-1995 period, with the greatest decreases occurring in February and March. These depth decreases have been accompanied by significant decreases in spring and summer snow cover duration over most of western Canada and the Arctic. The snow depth changes were characterized by a rather abrupt transition to lower snow depths in the mid-1970s that coincided with a well-documented shift in atmospheric circulation in the Pacific-North America sector of the Northern Hemisphere. (Au)

F, E, V
Atmospheric circulation; History; Mathematical models; Numeric databases; Ocean-atmosphere interaction; Quality assurance; Snow cover; Snowfall; Spatial distribution; Temporal variations

G08, G0822, G0823, G0824, G0821, G0825, G0826, G0827, G081
Atlantic Provinces; British Columbia; Canadian Arctic; Edmonton, Alberta; Gander, Newfoundland; Nouveau-Québec; Ontario; Prairie Provinces; Whitehorse, Yukon


Thermal features of the Mackenzie basin from NOAA AVHRR observations for summer 1994   /   Bussières, N.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 233-244, ill., maps)
References.
ASTIS record 51879.
Languages: English
Web: doi:10.3137/ao.400210
Libraries: ACU

A series of mid-afternoon Advanced Very High Resolution Radiometer (AVHRR) thermal radiance scenes were assembled in order to develop a better understanding of the complex energy and water processes leading to variations in surface temperature. An in-depth knowledge of the temperature variability is of interest to land surface process modelling and its application to the Mackenzie Global Energy and Water Cycle Experiment (GEWEX) Study (MAGS). Clear-sky land surface temperatures are estimated by applying a split window technique to remove atmospheric effects. A maximum land surface temperature map of the Mackenzie basin at 1-km scale for summer 1994 is produced. The patterns are related to land surface features and elevation. The basin's maximum land surface temperature patterns can be subdivided into three land zones (>=35°C, 33-34°C and 27-32°C) and a water dominated zone (20.5°C on average). The highest maximum temperature zone (>=35°C) corresponds to a combination of minimal vegetation, drier soils and low terrain. This zone is not in the southern part of the basin as might be speculated in the absence of these data, but in a wide low elevation corridor from west of Great Bear Lake along the Mackenzie River down to 50°N, 120°W. The maximum land surface temperatures tend to decrease with increasing vegetation density and surface moisture; they also decrease with elevation at a rate of -4.5°C/km. This is confirmed by weather station data. The AVHRR data extend this relationship to the 1200 - 2200 m altitude ranges, where there are no station data. The data suggest that elevation and land cover should be taken into account in the objective analysis (spatial interpolation) of station data. (Au)

E, A, H, F
Atmospheric temperature; Classification; Clouds; Conifers; Energy budgets; Geography; Instruments; Lakes; Land; Mapping; Mathematical models; Measurement; Plant cover; Remote sensing; Satellites; Snow; Solar radiation; Spatial distribution; Surface properties; Temperature; Temporal variations; Thermal properties; Wetlands

G0812, G0821, G0822, G0823
Alberta; Athabasca, Lake, Alberta/Saskatchewan; Athabasca, Lake, region, Alberta/Saskatchewan; British Columbia; Great Bear Lake, N.W.T.; Great Slave Lake, N.W.T.; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; N.W.T.; Saskatchewan


On the physical processes associated with the water budget and discharge of the Mackenzie basin during the 1994/95 water year   /   Cao, Z.   Wang, M.   Proctor, B.A.   Strong, G.S.   Stewart, R.E.   Ritchie, H.   Burford, J.E.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 125-143, ill., maps)
References.
ASTIS record 51873.
Languages: English
Web: doi:10.3137/ao.400204
Libraries: ACU

The Mackenzie River basin water budget and its discharge are investigated using the Canadian Meteorological Centre's Regional Finite Element/Global Environmental Multiscale (RFE/GEM) model-based analyses and observations. A comprehensive water budget analysis for the Mackenzie basin illustrates that the annual convergence of moisture flux over the region is positive, and that the moisture available for precipitation originates mainly from moisture transport across the south-west and north-west boundaries of the basin. In the summer, however, the basin's moisture supply comes mainly from local evaporation. It is found that major atmospheric forcings for discharge are predominantly determined by 1) the nature of the circulation systems and the availability of moisture, and 2) the alteration of moisture gradients through horizontal twisting by the wind fields. The second process is dominant over most of the 1994/95 water year. The basin scale discharge in the autumn (spring) is, to a large extent, related to cyclonic (anticyclonic) circulation systems through moisture redistribution. This occurs due to the horizontal twisting of moisture gradients by the wind fields and the corresponding moisture advection with horizontally-twisted moisture gradients. Over the southern Beaufort Sea, the overall storm frequency in the 1994/95 water year was very low compared with its climatology (Hudak and Young, this issue). However, this region was subjected to the highest percentage of Pacific-origin storms on record during the 1994/95 water year. Synoptic scale weather systems associated with major snowfall and critical spring snowmelt events in the 1994/1995 water year are also examined. Results show that one particular storm in the autumn of 1994 produced much of the initial snowfall for the basin and it was associated with a deep low pressure system providing a great deal of moisture flux into the basin through its western boundaries. It is also shown that a rapid spring snowmelt event in April 1995 was associated with a shallow high pressure system. The descending motion associated with this high pressure system and strong horizontal advection induced by a south-easterly low-level jet were two major elements that contributed to the rapid heating of the basin surface and the subsequent rapid melting of the snow. This unusual snowmelt event was a contributing factor to the annual discharge peak being earlier than normal. (Au)

F, E, D
Albedo; Atmospheric circulation; Atmospheric humidity; Atmospheric pressure; Climate change; Energy budgets; Evaporation; Hydrology; Mass balance; Mathematical models; Precipitation (Meteorology); River discharges; Runoff; Satellite photography; Snow; Snowmelt; Storms; Synoptic climatology; Winds

G0812, G03, G07
Arctic Ocean; Arctic Red River, N.W.T.; Athabasca, Lake, Alberta/Saskatchewan; Canadian Beaufort Sea; Great Bear Lake, N.W.T.; Great Slave Lake, N.W.T.; Liard River, British Columbia/N.W.T./Yukon; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; Peace River, Alberta/British Columbia; Peel River, N.W.T./Yukon


Hillslope hydrology and runoff processes in a Subarctic, subalpine environment   /   Carey, S.K.   Woo, M.-k. [Supervisor]
Hamilton, Ont. : McMaster University, 2000.
xvi, 206 p. : ill., maps ; 28 cm.
(ProQuest Dissertations & Theses publication, no. NQ72323)
ISBN 0-612-72323-2
Appendices.
References.
Thesis (Ph.D.) - McMaster University, Hamilton, Ont., 2000.
Indexed from a PDF file acquired from ProQuest Dissertations & Theses.
ASTIS record 54958.
Languages: English
Libraries: OONL

Within the subalpine zone of a subarctic basin, hydrological processes were studied on four hillslopes within 5 km² in an attempt to determine the factors that cause the variability in the magnitude and timing of water balance components. The hillslope was chosen as the scale of study as it links process operating at the point with streamflow, and exhibits strong contrasts in microclimate, vegetation, frost and soils, providing an ideal natural laboratory. Hillslopes showed strong asymmetry in the timing and magnitude of processes during the melt and summer period. On slopes with well drained soils and seasonal frost, vertical hydrological exchanges predominate over the entire year and slopes rarely contribute runoff for streamflow. In contrast, hillslopes underlain with permafrost and/or poorly drained soils with a capping organic layer produce strong lateral fluxes. Water balance information highlighted the principal factors that lead to differences in process magnitudes and timing. This information is important in understanding basin hydrology, as streamflow is a summation of lateral fluxes from slopes. The presence of ice-rich layers blocking soil interstices encourages runoff by restricting drainage. Runoff exhibits a two-layer flow system consisting of quickflow (pathways in the porous organic layer, pipes, rills, and interconnected depressions) and slowflow (pathways in underlying mineral soils and highly decomposed and compacted peat). Quickflow controls the shape and timing of the runoff hydrograph, which is influenced by properties of hillslope wetness and organic layer thickness. Recession analysis revealed variable source areas for runoff generation and highlighted the role of wetness-controlled hydrologic connectivity of a slope segment. Results from this thesis have implications for water resource inventories and predicting hydrologic behaviour of subarctic, subalpine hillslopes. (Au)

F, E, A, C, H
Ablation; Active layer; Aspect; Atmospheric temperature; Drainage; Evaporation; Flow; Frozen ground; Ground ice; Groundwater; Hydrology; Icings; Measurement; Melting; Moisture transfer; Movement; Permafrost; Plants (Biology); Rain; Rivers; Runoff; Seasonal variations; Slopes; Snow; Snow cover; Snow water equivalent; Snowmelt; Soil moisture; Soil percolation; Soil temperature; Solar radiation; Spatial distribution; Stream flow; Thawing; Theses; Thickness; Topography; Trees; Winds

G0811
Wolf Creek (60 37 15 N, 134 54 45 W) region, Yukon


The role of soil pipes as a slope runoff mechanism, Subarctic Yukon, Canada   /   Carey, S.K.   Woo, M.-K.
(Journal of hydrology (Amsterdam), v.233, no. 1-4, 12 June 2000, p. 206-222, ill., map)
ASTIS record 61359.
Languages: English
Web: doi:10.1016/S0022-1694(00)00234-1

Pipeflow in subarctic slopes provides a preferential runoff mechanism that bypasses the soil matrix, rapidly conveying water to the stream. Extensive soil piping occurs in the central Wolf Creek basin, Yukon, at the interface of the organic and mineral horizons. Flow in these pipes are ephemeral, transmitting water only when the water table is within or above the zone where pipes occur. During snowmelt, pipeflow began several days after the onset of surface runoff. Pipeflow contribution increased until ground thaw lowered the water tables, leaving matrix flow within the organic layer as the dominant mode of runoff. Pipeflow accounted for 21% of runoff during the 15 day melt period of 1997. Following melt, pipeflow recurred only during two intense summer rainstorms, each yielding different pipeflow response characteristics. During melt, pipeflow closely followed the daily snowmelt cycles and responded earlier than the integrated slope runoff. In the summer, pipeflow hydrographs rose and fell much quicker than direct storm runoff from the entire slope, which was dominated by fast matrix flow within the organic layer. Pipeflow contributing areas were relatively small, but their extent changed with hillslope wetness. Analysis revealed that the Manning flow formula can be combined with contributing areas to simulate pipeflow discharges. Unlike temperate environments where frozen ground is not a factor, the frost table position significantly controls the position of the phreatic surface, and must be considered in any models of pipeflow in permafrost slopes. (Au)

F, C, A, E, H
Aspect; Density; Drainage; Effects monitoring; Frozen ground; Groundwater; Hydrology; Mathematical models; Measurement; Meteorology; Peat; Permafrost; Plant cover; Precipitation (Meteorology); Runoff; Slopes; Snow; Snowmelt; Soil moisture; Soil temperature; Soil texture; Soils; Storms; Temporal variations; Thawing; Weather stations

G0811
Whitehorse region, Yukon; Wolf Creek (60 37 15 N, 134 54 45 W) region, Yukon


The role of blowing snow in the hydrometeorology of the Mackenzie River basin   /   Déry, S.J.   Yau, M.R. [Supervisor]
Montreal : McGill University, 2001.
xxi, 190 p. : ill., maps ; 28 cm.
(ProQuest Dissertations & Theses publication, no. NQ70002)
ISBN 0-612-70002-X
Appendix.
References.
Thesis (Ph.D.) - McGill University, Montreal, Quebec, 2001.
Indexed from a PDF file acquired from ProQuest Dissertations & Theses.
French résumé provided.
ASTIS record 55242.
Languages: English
Libraries: OONL

Despite being ubiquitous in the Mackenzie River Basin (MRB) of Canada, the role of snow in its energy and water budgets are still open to much speculation. This thesis presents a multi-scale analysis of the contribution of blowing snow to the hydrometeorology of the MRB. A climatology of adverse wintertime weather events is first presented and demonstrates that blowing snow events are rare within the forested sections of the MRB but become more frequent in the northern parts of the basin covered by Arctic tundra. It is these areas which experience the largest impacts of blowing snow transport and sublimation due to large-scale processes. To further assess the mesoscale and microscale effects of blowing snow to the northern regions of the MRB, the development of a bulk blowing snow model is then described. The single- and double-moment versions of the PIEKTUK blowing snow model are shown to produce equivalent results as a previous spectral version of the numerical model while operating about 100 times faster. The application of the double-moment PIEKTUK model (PIEKTUK-D) to a Canadian Arctic tundra site near the northern tip of the MRB reveals that blowing snow sublimation depletes ~3 mm snow water equivalent (swe) from the snowpack over a period of 210 days during the winter of 1996/1997 at Trail Valley Creek, Northwest Territories. Various assumptions on the state of the background thermodynamic profiles and their evolution during blowing snow, however, can yield significantly higher (>300%) rates of sublimation over the same period. PIEKTUK-D is then coupled to the Mesoscale Compressible Community (MC2) model for an interactive simulation of a ground blizzard at Trail Valley Creek. This coupled mesoscale simulation reveals that moistening and cooling of near-surface air associated with blowing snow sublimation is observed but mitigated in part by advective and entrainment processes. Combined, blowing snow sublimation and mass divergence are then shown to remove 1.4 mm swe per day during the Arctic ground blizzard at Trail Valley Creek. Nevertheless, blowing snow contributes to a lesser degree to the surface mass balance of the entire MRB by eroding 0.05 to 0.1 mm swe per year from the snowpack. (Au)

F, E
Atmospheric circulation; Atmospheric humidity; Atmospheric pressure; Atmospheric temperature; Blowing snow; Boundary layers; Energy budgets; Hydrology; Logistics; Mass balance; Mathematical models; Movement; Precipitation (Meteorology); Snow; Snow cover; Snow hydrology; Snow water equivalent; Snowdrifts; Snowfall; Snowstorms; Spatial distribution; Sublimation; Temporal variations; Thermodynamics; Theses; Thickness; Velocity; Visibility; Wind chill; Winds

G0812, G0811, G081, G02, G15
Antarctic regions; Arctic regions; Canadian Arctic; Mackenzie River region, N.W.T.; N.W.T.; Trail Valley Creek region, N.W.T.; Tuktoyaktuk Peninsula, N.W.T.; Yukon


Simulation of an Arctic ground blizzard using a coupled blowing snow-atmosphere model   /   Déry, S.J.   Yau, M.K.
(Journal of hydrometeorology, v. 2, no. 6, Dec. 2001, p. 579-598, ill., maps)
References.
ASTIS record 60283.
Languages: English
Web: doi:10.1175/1525-7541(2001)002<0579:SOAAGB>2.0.CO;2
Libraries: ACU

A ground blizzard occurred from 16 to 18 November 1996 in the northern sectors of the Mackenzie River basin of Canada and the adjacent Beaufort Sea. This hazardous event, accompanied by a low-level jet with wind speeds approaching 20 m/s and extensive blowing snow near the surface (but clear sky aloft), is forced by a strong sea level pressure gradient that forms between a rapidly intensifying anticyclone over the Nunavut and Northwest Territories of Canada and an intense depression over the frozen Arctic Ocean. The event is first simulated at a horizontal grid size of 18 km using the uncoupled Canadian Mesoscale Compressible Community (MC2) model. This experiment is shown to capture the rapid anticyclogenesis event within 2 hPa of its central sea level pressure and the blizzard conditions near the Canadian Arctic coastline and the Beaufort Sea. Meteorological conditions observed at Trail Valley Creek (TVC), a small Arctic tundra watershed in which ground blizzard conditions were experienced during the event, are also accurately reproduced by the uncoupled simulation with the notable exception of the blowing snow process. Thus, the mesoscale model is then coupled to the "PIEKTUK" blowing snow model, and a second simulation is conducted. This additional experiment reveals the presence of extensive blowing snow associated with a strong low-level jet over TVC and the adjacent frozen Beaufort Sea. Over the 2-day event, blowing snow sublimation and transport combined to erode 1.6 mm snow water equivalent from the surface mass balance of TVC. The concurrent moistening and cooling of near-surface air due to blowing snow sublimation emerge during the blizzard but to a lesser extent than in an idealized modeling framework, as a consequence of entrainment and advective processes. Therefore, blowing snow sublimation rates are evaluated to be 1.8 times larger than in the stand-alone application of the PIEKTUK model to the same data. (Au)

F, E, J, L, G
Airplanes; Atmospheric humidity; Atmospheric temperature; Blowing snow; Climate change; Effects of ice on climate; Energy budgets; Environmental impacts; Heat transmission; Hydrology; Mass balance; Mathematical models; Meteorology; Sea ice; Sedimentation; Snow cover; Snow hydrology; Snow water equivalent; Snowfall; Snowstorms; Sublimation; Tundra ecology; Visibility; Winds

G0812
Inuvialuit Settlement Region, N.W.T./Yukon; Mackenzie River region, N.W.T.; Trail Valley Creek region, N.W.T.; Tuktoyaktuk Peninsula, N.W.T.


Radiation balance of wetland tundra at northern treeline estimated from remotely sensed data   /   Duguay, C.R.   Rouse, W.R.   Lafleur, P.M.   Boudreau, L.D.
(Climate research, v. 13, no. 1, Sept. 7, 1999, p. 77-90, ill., maps)
References.
ASTIS record 61362.
Languages: English
Web: doi:10.3354/cr013077

Traditional methods of measuring surface net radiation involve point measurements that represent only a small area surrounding the instrumented sites. Remotely sensed spaceborne data offer the means by which to obtain estimates of the outgoing fluxes at the regional scale. The objective of this study was to estimate surface albedo, surface thermal exitance, and net radiation using Landsat Thematic Mapper (TM) data over wetland tundra at northern treeline near Churchill, Manitoba, Canada. Ground-based measurements of each component of the radiation balance were acquired at 5 locations coincident with 2 TM overpasses during summer 1991. Each location was representative of 1 of the major terrain types found in the Hudson Bay Lowlands (i.e. sedge-dominated wetland, upland lichen-heath, tundra lakes and ponds, willow/birch wetland, and open spruce-tamarack forest). The mean absolute differences between remote sensing estimates and field measurements (all sites combined) are 0.01 for albedo, 25.7 W/m² for thermal exitance, and 14.1 W/m² for net radiation. The 2 summer 1991 TM Images (June and August) were then used to examine within and between terrain type variations in surface net radiation during the growing season. TM Imagery from August 1984 and August 1991 were also utilized to investigate differences in surface fluxes between a dry year (1984) and a wet year (1991). Results indicate that surface wetness and, to a lesser extent, phenology are the 2 main factors controlling the radiation balance during the summer period in this subarctic tundra-forest landscape. (Au)

E, F, A, C, H, J
Albedo; Birches; Conifers; Energy budgets; Evaporation; Groundwater; Growing season; Hydrology; Instruments; Mapping; Measurement; Meteorological instruments; Plant cover; Plant-water relationships; Plants (Biology); Precipitation (Meteorology); Remote sensing; Satellites; Seasonal variations; Sedges; Soil moisture; Solar radiation; Surface properties; Taiga ecology; Temperature; Temporal variations; Thermal properties; Treeline; Tundra ecology; Tundra ponds; Weather stations; Wetlands; Willows

G0824
Churchill region, Manitoba; Hudson Bay region, Manitoba


Solar radiation in the Mackenzie River basin : retrieval from satellite measurements and evaluation of atmospheric models   /   Feng, J.   Leighton, H. [Supervisor]
Montreal : McGill University, 2001.
xxii, 194 p. : ill., maps ; 28 cm.
(ProQuest Dissertations & Theses publication, no. NQ78683)
ISBN 0-612-78683-8
Thesis (Ph.D.) - McGill University, Montreal, Quebec, 2001.
Indexed from a PDF file acquired from ProQuest Dissertations & Theses.
References.
French abstract also provided.
ASTIS record 57078.
Languages: English
Libraries: OONL

Accurate determination of solar flux at the top of the atmosphere (TOA), which can only be made from satellite observations, is essential for climate studies. In the present study, we developed a new technique to derive the solar fluxes at the TOA and at the surface from operational meteorological satellites. Two key steps in the technique are the narrowband to broadband (NTB) conversion and deriving the net solar flux at the surface from TOA observations. We developed a new NTB conversion algorithm from ScaRaB observations and radiation transfer model simulations. In deriving the net solar fluxes at the surface from TOA measurements, the effects of absorbing aerosols have been investigated. The technique described above has been applied to AVHRR data to derive a dataset of solar flux in the Mackenzie River Basin (MRB) for the Canadian GEWEX Enhanced Study (CAGES) period from June 1998 to September 1999. The derived net solar fluxes at the surface were evaluated with the surface measurements in the basin and good agreement was achieved. Radiation fields from two atmospheric models used in the Mackenzie GEWEX Study (MAGS) project, the Canadian Regional Climate Model (CRCM) and the Global Environmental Multiscale (GEM) model, were evaluated against satellite retrievals of radiation fluxes in the present study. It was found that the CRCM simulated the TOA reflected flux well in the MRB for the summer of 1994, but large biases were found in the partition of absorbed solar radiation between the atmosphere and the earth's surface. The net surface solar radiation was found to be overestimated by about 15% in the CRCM. Evaluation of the preliminary output from the new version of CRCM shows substantial improvement. Evaluation of radiation fields from the GEM model shows good agreement under clear skies, but under cloudy skies, the TOA albedo simulated by the GEM model in the MRB was about 30% lower than observations for the summer of 1999. (Au)

E, A, F
Aerosols; Albedo; Atmosphere; Atmospheric humidity; Climatology; Clouds; Data buoys; Equipment and supplies; Infrared remote sensing; Mathematical models; Measurement; Meteorological instruments; Ozone; Radiation budgets; Satellites; Seasonal variations; Snow; Snow cover; Solar radiation; Theses; Weather stations

G0812, G0811, G0821, G0822, G0823
Alberta, Northern; British Columbia, Northern; Great Slave Lake, N.W.T.; Havikpak Creek region, N.W.T.; Mackenzie River region, N.W.T.; Saskatchewan, Northern; Trail Valley Creek region, N.W.T.; Yukon, Northern


A comparision of solar radiation budgets in the Mackenzie River basin from satellite measurements and a regional climate model   /   Feng, J.   Leighton, H.G.   MacKay, M.D.   Bussières, N.   Hollmann, R.   Stuhlmann, R.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 221-232, ill., maps)
References.
ASTIS record 51878.
Languages: English
Web: doi:10.3137/ao.400209
Libraries: ACU

Using a new narrowband to broadband conversion algorithm developed specifically for the Mackenzie River basin (MRB), Advanced Very High Resolution Radiometer (AVHRR) data for the summer of 1994 have been analyzed to obtain the top-of-the-atmosphere (TOA) fluxes and the net surface solar radiation in the MRB. The AVHRR dataset contains mid-afternoon scenes from 21 June to 14 September 1994. In addition, the Scanner for Radiation Budget (ScaRaB) instrument, which flew on the METEOR-3 satellite, provided good coverage during the summer of 1994 with typically five passes over the northern part of the basin and three to four passes over the southern part of the basin each day. We merged the TOA fluxes from AVHRR with those from ScaRaB and then interpolated the observations (within ± 1.5 hours) to get the monthly means for each one-hour period during the daytime for June, July, August and September 1994. The monthly means of each one-hour average are compared with output from the Canadian Regional Climate Model (CRCM). The comparison shows that the CRCM simulated the TOA reflected fluxes well over the MRB. However, the differences in the partitioning of the absorbed energy between the surface and the atmosphere are large, the CRCM overestimating the surface net solar radiation budgets by about 15%. (Au)

E
Climatology; Clouds; Energy budgets; Instruments; Mathematical models; Measurement; Remote sensing; Satellites; Solar radiation; Spatial distribution

G0812
Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; N.W.T.


A six-year isotopic record of lake evaporation at a mine site in the Canadian Subarctic : results and validation   /   Gibson, J.J.   Reid, R.   Spence, C.
(CGU Hydrology Section/Eastern Snow Conference / Edited by M.R. Albert, T.D. Prowse, and S. Taylor. Hydrological processes, v. 12, no. 10/11, special edition, Aug./Sept. 1998, p.1779-1792, ill., maps)
References.
ASTIS record 41688.
Languages: English
Web: doi:10.1002/(SICI)1099-1085(199808/09)12:10/11<1779::AID-HYP694>3.3.CO;2-Z
Libraries: ACU

An isotopic method is applied in conjunction with a water balance method and the Penman combination method to estimate evaporation from a small high-closure lake near Yellowknife, Northwest Territories, Canada (62 03 N, 111 24 W). The study provides baseline hydrological information for assessment of tailings pond design and management at nearby mine sites, and notably, has enabled inter-comparison of several field-based evaporation methods and a standard climate approach in a subarctic setting. Water samples were collected at regular time-intervals to characterize temporal changes in the isotopic compositions of lake water, groundwater, precipitation, and atmospheric moisture, as part of a comprehensive monitoring programme during the open-water periods of 1991 to 1996. A non-steady isotope mass balance method is applied to estimate evaporation over individual sampling intervals ranging from five-days to three-weeks. Use of a relatively high-precision non-steady technique, in contrast to the commonly employed approach assuming isotopic steady-state, is feasible in the present setting due to pronounced seasonal evaporative enrichment in lake water (20-30 times analytical uncertainty of delta 18O). A comparative analysis reveals that the isotopic method is conservative relative to the Penman combination method, but less conservative than standard water balance, although estimates for the open-water period are in agreement to within 20% in both cases. Inter-annual variability in evaporation is revealed to be 30 to 50% greater than predicted from standard pan-to-lake algorithms, and of the same order of magnitude as annual snow water equivalent (~115-175 mm), which has important implications for design and management of tailings ponds in the area. (Au)

F, E, P, J
Acid rock drainage; Environmental impacts; Evaporation; Groundwater; Hydrology; Instruments; Isotopes; Lakes; Mass balance; Mathematical models; Meteorology; Mining; Tailings; Water level; Weather stations

G0812
Pocket Lake, N.W.T.; Yellowknife region, N.W.T.


Determining winter discharge based on hydraulic modeling   /   Hicks, F.E.   Healy, D.
(Canadian journal of civil engineering, v. 30, no. 1, Feb. 2003, p. 101-112, ill., maps)
References.
ASTIS record 54659.
Languages: English
Web: doi:10.1139/l02-031
Libraries: ACU

At present, the only accurate means of determining discharge under ice-affected conditions is by direct measurement, a costly undertaking that places field staff at personal risk. Consequently, winter discharge hydrographs are often based on interpolation between relatively infrequent direct measurements. This study explores the viability of using gradually varied flow hydraulic modeling to determine winter discharge. Based on an analysis of data obtained on the Mackenzie River near Fort Providence, Northwest Territories, and on the Athabasca River at Fort McMurray, Alberta, it appears that the errors associated with this approach could be as low as 3%. The potential applicability of stage-fall models based on hydraulic model data is also explored as a means to facilitate automated winter discharge measurements. Indications are that the viability of stage-fall modeling is highly dependent on identifying a suitable reach and establishing an adequate range of data. Hydraulic modeling has the potential to address both these issues. (Au)

F, G, E, J, R
Forecasting; Hydrology; Mathematical models; Measurement; Occupational health; River discharges; River ice; Safety; Seasonal variations; Stream flow

G0812, G0822
Athabasca River, Alberta; Fort McMurray region, Alberta; Fort Providence region, N.W.T.; Mackenzie River, N.W.T.


Storm climatology of the southern Beaufort Sea   /   Hudak, D.R.   Young, J.M.C.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 145-158, ill., 1 map)
References.
ASTIS record 51874.
Languages: English
Web: doi:10.3137/ao.400205
Libraries: ACU

Building on the expertise from the Beaufort Weather Office, an objective method of identifying storm periods in the southern Beaufort Sea area based on surface wind speed criteria was developed. Algorithms that used hourly observations from Tuktoyaktuk and Sachs Harbour were trained to identify storm periods over the southern Beaufort Sea. The Master List produced by Eid and Cardone (1992) was used as a training set to tune the algorithms. A check with independent observations taken by a drilling platform verified the soundness of the approach. The National Centers for Environmental Prediction (NCEP) reanalysis dataset was used to characterize storm type. In doing so, upper air data were introduced to the classification process. The important variables were 50-kPa wind speed and direction, and the 85-kPa temperature. The former variable is a reflection of the steering current of the storm systems while the latter is related to airmass characteristics within the storm system. The algorithms were applied to the 1970 to 1995 time period for the months of June to November inclusive. On the average, there were 14 storms per storm season, with a standard deviation of 5. The years 1976 to 1982 were the most stormy with an average of 19 storms per storm season. There was no discernable trend in the storm frequency over the 25-year period. By month, October had the highest storm frequency, July the lowest. The average 50-kPa wind direction during storm periods was used to classify the storms as Arctic, Pacific or Irregular. The three storm types were further subdivided based on the average 50-kPa wind speed and the 85-kPa temperature change. Overall, 58% of the storms were Arctic, 27% Pacific and 15% Irregular. There was an indication that Pacific storms have become less frequent in recent years. This decrease was the result of an absence of Pacific storms associated with relatively small net 85-kPa temperature changes. The data were then stratified by El Niño episodes. There were more storms during ElNiño years because of an increase in Arctic storms. However, despite this over all increase, there was a decrease in the percentage of Arctic storms associated with strong cold air outbreaks. This storm information was used to aid in the interpretation of two studies related to conditions in 1994. The first was the Beaufort and Arctic Storms Experiment and the second the 1994/95 water year of the Mackenzie River basin. (Au)

E
Climate change; Storms; Winds

G07, G0812, G02, G05
Arctic regions; Canadian Beaufort Sea; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; North Pacific Ocean; Sachs Harbour (Settlement), N.W.T.; Tuktoyaktuk, N.W.T.


Snowmelt and runoff in a Subarctic mountain basin   /   Janowicz, J.R.   Gray, D.M.   Pomeroy, J.W.
(Proceedings of the Hydro-Ecology Workshop on the Arctic Environmental Strategy Action on Water, May 1996, Banff, Alberta / Edited by D. Milburn. NHRI symposium, no. 16, 1997, p. 303-320, ill., 1 map)
References.
ASTIS record 41439.
Languages: English
Libraries: ACU

Spring runoff is usually the most important hydrologic event of the year in streams draining subarctic regions. The magnitude and timing of the runoff event is controlled by the distribution of snow water equivalent over the basin, the rate of snowmelt and the delivery of water to the stream channel. An analysis of snow accumulation and snowmelt runoff was carried out for Wolf Creek, a small (195 km²) basin in the headwaters of the Yukon River. The upper portion of the basin is wind-swept tundra, middle elevations are covered with deciduous shrubs and the lower portion is boreal forest. Basin snow water equivalent and daily melt rates were estimated at three sites and extrapolated to the three corresponding elevation/vegetation bands. Estimated snowmelt runoff from each elevation band was compared to streamflow measurements during melt for two consecutive seasons. Though the two snow accumulation seasons were similar, the magnitude of runoff during the snowmelt period differed by approximately three-hundred percent. The effects of variations in the rate of snowmelt and the infiltrability of frozen soils on the potential runoff and the errors in estimating the components of the spring water balance are examined as possible causes for the difference. (Au)

F, E, C
Ablation; Accumulation; Atmospheric humidity; Atmospheric temperature; Databases; Evaporation; Frozen ground; Groundwater; Hydrological stations; Meteorology; Rain; River discharges; Runoff; Snow; Snow water equivalent; Snowmelt; Soil moisture; Soil percolation; Stream flow; Temporal variations; Winds

G0811
Whitehorse region, Yukon; Wolf Creek (60 37 15 N, 134 54 45 W), Yukon; Yukon River, Alaska/Yukon


Summer convection and lightning over the Mackenzie River basin and their impacts during 1994 and 1995   /   Kochtubajda, B.   Stewart, R.E.   Gyakum, J.R.   Flannigan, M.D.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 199-220, ill., maps)
References.
ASTIS record 51877.
Languages: English
Web: doi:10.3137/ao.400208
Libraries: ACU

Lightning activity over the Mackenzie basin has been examined for the summers of 1994 and 1995. In recent years, the lightning network operating in the Northwest Territories has detected an average of 118 K strikes per season. Positive lightning strikes (defined as lightning discharges lowering positive charge to the earth) typically comprise 12% of the total. The lightning activity during 1994 was approximately 20% below normal, while in 1995, it was 53% below normal. However, the fraction of positive lightning strikes was 25.6% during 1995. The lightning was linked to synoptic conditions favouring severe storm development, especially those tied to the diurnal cycle. As a consequence of the lightning, as well as the very dry surface conditions, record forest areas were burned. In the Northwest Territories alone, forest fires burned 3 Mha in 1994 and 2.8 Mha in 1995. (Au)

E, F, J
Air pollution; Atmospheric circulation; Atmospheric electricity; Climatology; Clouds; Detection; Diurnal variations; Forest fires; Lightning; Maps; Precipitation (Meteorology); Rain; Seasonal variations; Storms; Synoptic climatology; Temporal variations; Visibility

G0812, G0821, G0822, G0823
Alberta; British Columbia; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; N.W.T.; Saskatchewan; Yukon


Characteristics of the water vapour transport over the Mackenzie River basin during the 1994/95 water year   /   Liu, J.   Cho, H.-R.   Stewart, R.E.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 101-111, ill.)
References.
ASTIS record 51871.
Languages: English
Web: doi:10.3137/ao.400202
Libraries: ACU

The National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data were used to calculate the moisture flux convergence over the Mackenzie River basin (MRB) for a 10-year period from 1987 to 1996. The analysis of these results indicates that the 1994/95 water year was associated with the least amount of water vapour transport into the MRB over this selected period. This arose due to some unique features in the vertical structure of water vapour transport. In particular, the average annual level of maximum water vapour transport occurred at 700 hPa during 1994/95; this is higher than the 850-hPa level found for other years. Because of the lower humidity at higher levels in the atmosphere, the magnitude of the most significant water vapour transport was therefore less. Detailed analyses of the monthly data for the 1994/95 water year illustrated that the decrease in water vapour transport arose, in part, because of the year's deep mixed boundary layer attributable to its warm temperatures and dry surface conditions. Of course, the magnitude of the monthly moisture flux convergence changed substantially during this water year. The largest contribution occurred from July to October 1995, with the maximum in July. Two other peaks were found in October 1994 and February 1995. The moisture flux convergence at the transition period between seasons (May and June) was very weak and sometimes even negative. To understand better the components of the water balance for this water year, observational precipitation data were used to estimate evaporation. The water balance for this specific water year also showed that the precipitation in the 1995 summer was due mainly to the moisture flux convergence into the MRB, instead of the evaporation found in other studies. Correlation coefficients between the moisture flux convergence and precipitation were much higher for this water year than in other studies. The horizontal distribution of the moisture flux convergence across the basin during this water year displayed a band of high values between the Rocky Mountains and Great Bear Lake and another band of high values at the southern edge of the basin, which is closely linked with the topography in the MRB. (Au)

E, F
Atmospheric humidity; Atmospheric pressure; Boundary layers; Evaporation; Hydrology; Mass balance; Mathematical models; Precipitation (Meteorology); Spatial distribution; Water vapour; Water vapour; Winds

G0812
Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.


The water balance climatology of the Mackenzie basin with reference to the 1994/95 water year   /   Louie, P.Y.T.   Hogg, W.D.   MacKay, M.D.   Zhang, X.   Hopkinson, R.F.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 159-180, ill., maps)
References.
ASTIS record 51875.
Languages: English
Web: doi:10.3137/ao.400206
Libraries: ACU

This project attempted to develop an accurate baseline climatology for the Mackenzie basin suitable for modelling and other evaluation applications in the Mackenzie GEWEX (Global Energy and Water Cycle Experiment) Study. Particular attention and effort were applied to adjusting the observed station precipitation data in order to minimize systematic measurement errors. Various geostatistical methods were applied to interpolate the station data onto a uniform grid. This resulted in datasets of 50-km grid square values for mean monthly temperature and monthly total precipitation for the years 1950 to 1997 inclusive. An independent estimate of basin evapotranspiration was derived using an empirical model (Morton, 1983) to generate similar grid square values of monthly total evapotranspiration for the years 1953 to 1996 inclusive. From the grid square datasets, we computed the mean annual basin temperature (T) to be -3.4°C, the mean annual basin precipitation (P) to be 421 mm and the mean annual basin evapotranspiration (E) to be 277 mm. A simple water balance was applied to test the consistency of the P and E fields with the observed basin discharge (Q). For the 24-year period 1972 to 1995, the mean annual residual (P-E-Q) for the water balance was -28.4 mm. This residual is a combination of errors in the three water balance components and the assumption of zero annual storage. It is within the estimation errors associated with the measurement and analysis methods used. Further analysis on the correlation of Q with the total basin net surface moisture supply (P-E) showed that P and (P-E) are most strongly correlated with Q with a 3-month lag, i.e., a discharge water-year of October-September corresponds best with a (P-E) year of July-June. In examining the seasonal correlation of T and E with Q, we found that summer T was significantly correlated with annual Q but there was no significant correlation between any seasonal E or annual Q. This suggests that although the Morton model estimates of E provided a reasonable magnitude for the long-term annual basin water balance, it cannot be considered reliable for year-to-year or shorter-term estimates of the basin evapotranspiration. In examining the 1994/95 water year, it was found to be the lowest discharge year (October-September) in the observed record. This is consistent with the 3-month lagged climate data year (July-June) which for 1994/95 has the largest (P-E) anomaly; it is also the driest year since 1950 having the warmest summer months on record and the third lowest precipitation on record. To demonstrate a practical application of the climate datasets generated by this study, we constructed a multilinear regression model for annual (October-September) discharge based on annual (July-June) basin precipitation and summer temperature. The resulting linear model estimated the annual discharge remarkably well, explaining 61% of the variance for this period. Using this model we were able to reconstruct an estimate of annual discharge back to 1950. (Au)

E, F
Atmospheric temperature; Climate change; Climatology; Evaporation; Hydrology; Mathematical models; Measurement; Meteorological instruments; Precipitation (Meteorology); River discharges; Weather stations

G0812, G0821, G0811, G0822, G0823
Alberta; Arctic Red River, N.W.T.; Athabasca, Lake, Alberta/Saskatchewan; British Columbia; Great Bear Lake, N.W.T.; Great Slave Lake, N.W.T.; Liard River, British Columbia/N.W.T./Yukon; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; Peace River, Alberta/British Columbia; Peel River, N.W.T./Yukon; Saskatchewan; Yukon


Downscaling the hydrological cycle in the Mackenzie Basin with the Canadian Regional Climate Model   /   MacKay, M.D.   Stewart, R.E.   Bergeron, G.
(Atmosphere-ocean, v. 36, no. 3, Sept. 1998, p. 179-211, ill., maps)
References.
ASTIS record 48869.
Languages: English
Libraries: ACU

The Canadian Regional Climate Model (CRCM) has been nested within the Canadian Centre for Climate Modelling and Analysis' second generation General Circulation Model (GCM), for a single month simulation over the Mackenzie River Basin and environs. The purpose of the study is to assess the ability of the higher resolution CRCM to downscale the hydrological cycle of the nesting GCM. A second 1-month experiment, in which the CRCM was nested within analyzed fields of a global data assimilation system, was also performed to examine the sensitivity of the basin moisture budget to atmospheric lateral boundary forcing. We have found that the CRCM can produce realistic lee cyclogenesis, preferentially in the Liard sub-basin, along with associated circulation and precipitation patterns, as well as an improved rainshadow in the lee of the Rocky Mountains compared to the GCM. While these features do quantitatively affect the monthly average climate statistics, the basin scale moisture budgets of the models were remarkably similar, though some of this agreement is due to compensating errors in the GCM. Both models produced excessive precipitation compared to a recent climatology for the region, the cause of which is traced to lateral boundary forcing. A second experiment, identical to the first except that the CRCM was forced with analyzed fields at the lateral boundaries, produced a qualitatively different basin moisture budget, including a much more realistic precipitation field. Errors in the moisture budget of the first experiment appear to be associated with the poor representation of the Aleutian Low in the GCM, and do not appear to be strongly connected to (local) surface processes within the models. This suggests that an effective strategy for modelling the hydrological cycle of the Mackenzie Basin on the fast climate timescale - a major requirement of the Mackenzie GEWEX Study - will involve nesting the CRCM within analysed (or re-analyzed) atmospheric fields. (Au)

E, F, J
Atmospheric circulation; Climate change; Climatology; Evaporation; Hydrology; Mathematical models; Ocean-atmosphere interaction; Precipitation (Meteorology); Soil moisture

G0812
Liard River region, British Columbia/N.W.T./Yukon; Mackenzie River region, N.W.T.


Hydrological processes and runoff at the Arctic treeline in northwestern Canada   /   Marsh, P.   Quinton, W.L.   Pomeroy, J.W.   Global Energy and Water Experiment [Sponsor]   Canada. Environment Canada [Sponsor]
In: Project reports 1994-95 (including attachments) : Arctic Environmental Strategy NWT Water Component / Northern Affairs Program (Canada). Water Resources Division. - Yellowknife, N.W.T. : Water Resources Division, Indian and Northern Affairs, 1995, [30] p., ill., maps
In: Proceedings : Tenth International Northern Research Basins Symposium and Workshop, Spitsbergen, Norway, August 28 to September 3, 1994 / Edited by K. Sand and A. Killingtveit. - [S.l. : s.n., 1994], p. 368-397, ill., maps
References.
ASTIS record 41664.
Languages: English
Libraries: ACU

Models of snow accumulation, melt, vertical meltwater percolation, and evaporation, were used in conjunction with observations of basin snow cover and hillslope hydrology to explain certain aspects of the runoff regime, as well as the annual and daily water balance of an Arctic treeline site in northwestern Canada. These studies indicated that snowfall was the largest input to the basin, accounting for 58% of the annual total. However, transport during blowing snow was also significant, accounting for 16% of inputs, while sublimation removed 10% of annual inputs. Although the majority of annual precipitation was released over a brief period in the spring, the initiation of runoff was delayed by the processes of vertical percolation of meltwater into the snow and frozen soil infiltration. As a result of these processes, basin water storage increased dramatically during the early melt period, with over 150 mm of melt occurring before streamflow began. The occurrence of mineral hummocks greatly affected the transfer of meltwater from late lying snow patches, with organic water tracks responsible for rapidly transporting water to the stream channel. Over 90% of annual runoff occurred during the melt period. Surprisingly, however, discharge only removed 44% of snow stored in the basin at the start of melt. The remaining meltwater was stored in the basin, with the majority supplying evaporation, which removed 62% of water inputs to the basin. (Au)

F, E, A, H, J
Accumulation; Atmospheric temperature; Blowing snow; Evaporation; Hummocks; Hydrology; Mass balance; Mathematical models; Plant distribution; Runoff; Snow; Snow cover; Snowdrifts; Snowmelt; Snowpatches; Soil percolation; Solar radiation; Sublimation; Topography; Treeline

G0812
Inuvik, N.W.T.; Siksik Creek region, N.W.T.; Trail Valley Creek region, N.W.T.; Trail Valley Creek, N.W.T.; Tuktoyaktuk, N.W.T.


Snow/soil heat and mass fluxes at an arctic treeline site   /   Marsh, P.   Pomeroy, J.W.
In: Project reports 1994-95 (including attachments) : Arctic Environmental Strategy NWT Water Component / Northern Affairs Program (Canada). Water Resources Division. - Yellowknife, N.W.T. : Water Resources Division, Indian and Northern Affairs, 1995, [1] p.
Abstract only.
European Conference on Global Energy and Water Cycles, Royal Society, London, England, 1994.
ASTIS record 41667.
Languages: English
Libraries: ACU

When snowmelt percolates into the underlying snowcover it may freeze, fill irreducible liquid water storages, or be available for runoff. In temperate areas, the portion of the meltwater which freezes is relatively small. However, in Arctic areas it is very large due to the cold snow and the existence of permafrost which results in a large negative ground heat flux that removes energy from the snowpack during the melt period. These processes have important implications for delaying runoff and limiting its magnitude. In addition, this extends the period of high surface albedo, with resulting impact on the regional radiational balance. The infiltration of meltwater into the snow/soil, and the subsequent heat fluxes have been studied at a Canadian GEWEX station north of Inuvik, Northwest Territories. Field measurements and model results demonstrate that: (1) the snow/soil thermal regime at the end of winter is dependent on the snow depth, which is related to the redistribution and sublimation by blowing snow, and therefore on the spatial configuration of tundra and taiga surfaces. (2) change in snow/soil heat storage is a significant component of the surface energy balance during the melt period, with differences between various tundra and taiga surfaces. These regional variations must be accounted for when modelling snowcover energy balance, removal, and runoff. (Au)

F, C
Heat budgets; Heat transmission; Mass balance; Mathematical models; Runoff; Snow; Snow cover; Soil percolation; Soils; Sublimation; Taiga ecology; Thermal properties; Treeline; Tundra ecology

G0812
Inuvik region, N.W.T.


Meltwater fluxes at an Arctic forest-tundra site   /   Marsh, P.   Pomeroy, J.W.
(Mapping regional snow distribution in northern basins, Inuvik area, March 1997 / Edited by P. Marsh, J. Pomeroy, A. Pietroniro, N. Neumann, and T. Nelson. NHRI contribution, no. 97006, 1997, [19] p., ill., maps)
(Special issue of the Canadian Geophysical Union - Hydrology Section / Edited by T.D. Prowse. Hydrological processes, v. 10, no. 10, Oct. 1996, p.1383-1400, ill., maps)
References.
ASTIS record 41682.
Languages: English
Web: doi:10.1002/(SICI)1099-1085(199610)10:10<1383::AID-HYP468>3.0.CO;2-W
Libraries: ACU

Models of surface energy balance and snow metamorphism are utilized to predict the energy and meltwater fluxes at an Arctic site in the forest-tundra transition zone of north-western Canada. The surface energy balance during the melt period is modelled using an hourly bulk aerodynamic approach. Once a snowcover becomes patchy, advection from the bare patches to the snow-covered areas results in a large spatial variation in basin snowmelt. In order to illustrate the importance of small-scale, horizontal advection, a simple parameterization scheme using sensible heat fluxes from snow free areas was tested. This scheme estimates the maximum horizontal advection of sensible heat from the bare patches to the snow-covered areas. Calculated melt was routed through the measured snowcover in each landscape type using a variable flow path, meltwater percolation model. This allowed the determination of the spatial variability in the timing and magnitude of meltwater release for runoff. Model results indicate that the initial release of meltwater first occurred on the shallow upland tundra sites, but meltwater release did not occur until nearly two weeks later on the deep drift snowcovers. During these periods of melt, not all meltwater is available for runoff. Instead, there is a period when some snowpacks are only partially contributing to runoff, and the spatial variation of runoff contribution corresponds to landscape type. Comparisons of melt with and without advection suggests that advection is an important process controlling the timing of basin snowmelt. (Au)

F, A, C, H, J
Energy budgets; Forest ecology; Heat transmission; Mathematical models; Plant distribution; Runoff; Snow cover; Snow hydrology; Snow metamorphism; Snowmelt; Snowpatches; Soil percolation; Topography; Tundra ecology

G0812
Trail Valley Creek region, N.W.T.; Trail Valley Creek, N.W.T.


Water and energy fluxes in the lower Mackenzie Valley, 1994/95   /   Marsh, P.   Onclin, C.   Neumann, N.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 245-256, ill., 1 map)
References.
ASTIS record 51880.
Languages: English
Web: doi:10.3137/ao.400211
Libraries: ACU

The 1994/95 water year in the lower Mackenzie Valley was an extraordinary year hydrologically, with the important winter to summer transition being the earliest on record. Unlike more temperate areas, the northern water year is dominated, to a great extent, by this onset of spring which results in the melting of nearly half of the annual precipitation over a period of a few weeks, initiates the thawing of the river and lake ice and the soil active layer, and marks the beginning of the evaporation season. An early winter to summer transition occurred at two small research basins in the Inuvik area and at the East Channel of the Mackenzie River Delta. At the research basins, for example, the spring of 1994/95 had the earliest onset of continuous above-freezing air temperatures, removal of the snow cover, and initiation of runoff. Consideration of the entire water year at the research basins demonstrates that rain and snow were nearly equal in magnitude, evaporation exceeded runoff, and the annual change in storage was negative to near zero. This negative change in storage was related to the long, snow-free evaporation season, above-average air temperatures, and below-normal precipitation. The unusual winter to summer transition on the Mackenzie River in the eastern portion of the Mackenzie Delta was, in many ways, even more remarkable than that in the research basins. Earlier work had suggested that the timing of the spring breakup was very consistent from year to year. An analysis of the timing of breakup from the early 1960s to the late 1990s, however, shows a trend towards earlier spring breakup, with the mean for the 1990s being nine days earlier than that for the 1960s, and with the 1995 breakup being the earliest on record. Such an early breakup is not only an indication of warm local conditions, but of warm temperatures and an early runoff event over the more southerly areas of the Mackenzie basin. A companion Mackenzie Global Energy and Water Cycle Experiment study illustrates the importance of a high pressure circulation pattern centred east of the basin to this early melt event. (Au)

F, E, G
Active layer; Atmospheric circulation; Atmospheric pressure; Atmospheric temperature; Breakup; Energy budgets; Evaporation; Hydrology; Mass balance; Precipitation (Meteorology); River discharges; River ice; Rivers; Snow cover; Snowmelt; Stream flow; Water level

G0812, G082
East Channel (Mackenzie River), N.W.T.; Mackenzie Delta, N.W.T.; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; N.W.T.


Snowmelt processes and runoff at the Arctic treeline : ten years of MAGS research   /   Marsh, P.   Pomeroy, J.   Pohl, S.   Quinton, W.   Onclin, C.   Russell, M.   Neumann, N.   Pietroniro, A.   Davison, B.   McCartney, S.
In: Cold region atmospheric and hydrologic studies : the Mackenzie GEWEX experience. Volume 2 : hydrologic processes / Edited by Ming-ko Woo. - New York : Springer, 2008, ch. 6, p. 97-123, ill., maps
References.
ASTIS record 68674.
Languages: English
Web: doi:10.1007/978-3-540-75136-6
Libraries: ACU

Under the Mackenzie GEWEX Study, extensive snowmelt and runoff research was carried out at the Trail Valley and Havikpak Creek research basins at the tundra-forest transition zone near Inuvik, Northwest Territories. Process based research concentrated on snow accumulation, the spatial variability of energy fluxes controlling melt, local scale advection of sensible heat from snow-free patches to snow patches, percolation of meltwater through the snowpack, storage of meltwater in stream channels, and hillslope runoff. Building on these studies, process based models were improved, as shown by a better ability to model changes in snow-covered area during the melt period. In addition, various landsurface and hydrologic models were tested, demonstrating an enhanced capability to model melt related runoff. Future research is required to accurately model both snow-covered area and runoff at a variety of scales and to incorporate topographic and vegetation effects correctly in the models. (Au)

F, H, E, A
Aerial photography; Albedo; Blowing snow; Evaporation; Heat transmission; Hummocks; Hydrological stations; Hydrology; Mapping; Mathematical models; Measurement; Meteorology; Peat; Plant-water relationships; Precipitation (Meteorology); River discharges; Runoff; Satellite photography; Seasonal variations; Shrubs; Snow surveys; Snowmelt; Snowpatches; Solar radiation; Spatial distribution; Stream flow; Surface properties; Temporal variations; Topography; Treeline; Weather stations; Winds

G0812
Havikpak Creek region, N.W.T.; Havikpak Creek, N.W.T.; Mackenzie River region, N.W.T.; Trail Valley Creek region, N.W.T.; Trail Valley Creek, N.W.T.


Rehabilitation and analysis of Canadian daily precipitation time series   /   Mekis, E.   Hogg, W.D.
(Atmosphere-ocean, v. 37, no. 1, Mar. 1999, p. 53-85, ill., maps)
References.
ASTIS record 48871.
Languages: English
Libraries: ACU

The goal of this project was to develop adjustment procedures to use daily resolution data to generate high quality time series of precipitation and to perform regional trend analyses on the resulting datasets. A total of 69 locations, most with data covering the period 1900-96 were used. Data availability in much of the Canadian Arctic was restricted to 1948-96. By using daily data, improved corrections to precipitation data, not practical with monthly data, could be implemented. For each of three rain gauge types, corrections to account for wind undercatch and evaporation were implemented. Gauge specific wetting loss corrections were applied for each rainfall event. For snowfall, ruler measurements were used throughout the time series, to minimize potential discontinuities introduced by the adoption of Nipher shielded snow gauge measurements in the mid-1960s. Density corrections based upon coincident ruler and Nipher measurements were applied to all ruler measurements. Where necessary, records from neighbouring stations were joined employing a technique based on a simple ratio of observations. The adjustment procedures used remove systematic biases due to changes in the measurement program but do not account for inhomogeneities related to local site changes etc. It is assumed that such local changes introduce random inhomogeneities which are smoothed by combining the results from numerous stations. Work to adjust data from about 500 stations and generate monthly grids or maps is well underway but preliminary trend results were examined for this project by grouping stations by region. Regional time series of normalized anomalies are computed as the arithmetic mean of stations within the region. Annual and seasonal graphs of national and regional time series are presented. The national time series shows an increase in precipitation of 1.7% of mean/decade over 1948-95. The greatest increase is in the autumn. For the same period, Canada north of 55°N showed an increase of 2.3% of mean/decade, more than the south, but much less than the 4-5% of mean/decade suggested by Groisman and Easterling (1994). The ratio of liquid to solid precipitation for Canada has declined slightly over the 1948-95 period. (Au)

E, F
Blowing snow; Climate change; History; Mathematical models; Measurement; Meteorological instruments; Numeric databases; Precipitation (Meteorology); Snowfall

G08, G081
Canada; Canadian Arctic


Classification of hydrologically significant land cover in permafrost basins   /   National Hydrology Research Institute (Canada)   Pietroniro, A.   Prowse, T.D.   Marsh, P.   Pomeroy, J.W.   Global Energy and Water Experiment [Sponsor]   Canada. Indian and Northern Affairs Canada [Sponsor]   Science Institute of the Northwest Territories [Sponsor]   Polar Continental Shelf Project (Canada) [Sponsor]
In: Project reports 1994-95 (including attachments) : Arctic Environmental Strategy NWT Water Component / Northern Affairs Program (Canada). Water Resources Division. - Yellowknife, N.W.T. : Water Resources Division, Indian and Northern Affairs, 1995, [3] p.
References.
Proceedings, Canadian Symposium on Remote Sensing.
ASTIS record 41666.
Languages: English
Libraries: ACU

Scientists at the National Hydrology Research Institute (NHRI) have conducted research on the unique hydrologic characteristics of the Mackenzie Basin for several decades, with study sites in major hydrologically representative regions, including near Fort Simpson and Inuvik. To compensate for problems associated with the remoteness and geographic scale of these regions, remote sensing has been used to derive appropriate data for hydrologic simulation. Specifically, terrain types deemed significant to hydrologic response in wetland-dominated and tundra regimes, were discriminated using supervised, unsupervised and hybrid classifications schemes, as well as principle component analysis. The terrain types which dominate the hydrologic response of both regions could be best discriminated using the hybrid technique. The terrain classifications were then input to Grouped Response Unit (GRU) based hydrologic models, the reliability of which are highly dependent on the quality of hydrologic-terrain typing. Comparison of the results for the classification schemes and their suitability as a basis of applying the GRU modelling approach are discussed. (Au)

F, C
Classification; Hydrology; Landforms; Mathematical models; Permafrost; Remote sensing; Runoff; Watersheds

G0812
Fort Simpson region, N.W.T.; Liard River, British Columbia/N.W.T./Yukon; Mackenzie River, N.W.T.


A case study of the CAGES hail storm at Fort Simpson, Northwest Territories   /   Plette, N.C.   Yau, P.M.K. [Supervisor]
Montreal, Quebec : McGill University, 2001.
xi, 56 p., v : ill., maps ; 28 cm.
(ProQuest Dissertations & Theses publication, no. MQ75336)
ISBN 0-612-75336-0
References.
Thesis (M.Sc.) - McGill University, Montreal, Quebec, 2001.
Indexed from a PDF file acquired from ProQuest Dissertations & Theses.
ASTIS record 55277.
Languages: English
Libraries: OONL

This research focuses on the numerical simulation of a rare, high-latitude hail storm observed during the CAGES (Canadian GEWEX Enhanced Study) field experiment. On 11 May 1999, a shortwave trough moved northward from British Columbia and continued its passage over the Northwest Territories. A hail storm developed in an environment of small convective available potential energy. To understand the processes responsible for the formation of the storm, the Canadian Mesoscale Compressible Community Model (MC2) is used to simulate the case. The addition of a second soil type to the lower boundary of the model allows for a realistic simulation of the location and time of the storm. The results indicate that the dynamics associated with the shortwave trough, coupled with diurnal heating effects over the more realistic soil type, produced the weakly-forced hail storm that passed directly over Fort Simpson, Northwest Territories. (Au)

E, C, J
Diurnal variations; Energy budgets; Heat transmission; Ionosphere; Mathematical models; Precipitation (Meteorology); Soils; Storms; Temperature; Theses; Weather forecasting

G0812
Fort Simpson, N.W.T.


Snow accumulation and sublimation at the tundra-taiga transition   /   Pomeroy, J.W.   Marsh, P.   Gray, D.M.   Global Energy and Water Experiment [Sponsor]   Canada. Indian and Northern Affairs Canada [Sponsor]   Science Institute of the Northwest Territories [Sponsor]   Polar Continental Shelf Project (Canada) [Sponsor]
In: Project reports 1994-95 (including attachments) : Arctic Environmental Strategy NWT Water Component / Northern Affairs Program (Canada). Water Resources Division. - Yellowknife, N.W.T. : Water Resources Division, Indian and Northern Affairs, 1995, [1] p.
Abstract only.
European Conference on Global Energy and Water Cycles, Royal Society, London, England, 1994.
ASTIS record 41668.
Languages: English
Libraries: ACU

The processes of snow accumulation differ between open and forested areas. Wind transport of snow dominates the development of snowcover on the tundra, whilst relatively little wind transport of snow occurs in taiga forests. Redistribution of snow by wind affects the spatial distributions of depth and density. Sublimation of blowing snow diminishes the snow water equivalent over broad areas. Redistribution and sublimation are restricted in taiga forests because of lower wind speeds. Snow redistribution in mixed tundra and taiga at the Canadian GEWEX Station north of Inuvik, Northwest Territories has been modelled by physically-based algorithms that use standard climatological and land cover data to calculate the transport and sublimation fluxes of blowing snow and the snow-surface erosion flux. Redistribution of snow occurs over scales from metres to several kilometres and is verified by extensive field measurements. The model outputs are compared to field measurements that indicate about 70% of snow is removed from open tundra by blowing snow and that roughly half of this snow sublimates in transit. The ratio of sublimated snow to that which is redeposited depends upon the length of tundra fetch and therefore upon the scale and spatial configuration of tundra and taiga surfaces in the region. (Au)

F, E, J
Accumulation; Blowing snow; Mathematical models; Snow; Snow cover; Snow water equivalent; Spatial distribution; Sublimation; Taiga ecology; Tundra ecology; Winds

G0812
Inuvik region, N.W.T.


Application of a distributed blowing snow model to the Arctic   /   Pomeroy, J.W.   Marsh, P.   Gray, D.M.
(Mapping regional snow distribution in northern basins, Inuvik area, March 1997 / Edited by P. Marsh, J. Pomeroy, A. Pietroniro, N. Neumann, and T. Nelson. NHRI contribution, no. 97006, 1997, [16] p., ill.)
(Hydrological processes, v. 11, no. 11, Sept. 1997, p.1451-1464, ill.)
References.
ASTIS record 41686.
Languages: English
Web: doi:10.1002/(SICI)1099-1085(199709)11:11<1451::AID-HYP449>3.0.CO;2-Q
Libraries: ACU

Transportation, sublimation and accumulation of snow dominate snow cover development in the Arctic and produce episodic high evaporative fluxes. Unfortunately, blowing snow processes are not presently incorporated in any logical or meteorological models. To demonstrate the application of simple algorithms that represent blowing snow processes, monthly snow accumulation, relocation and sublimation fluxes were calculated and applied in a spatially distributed manner to a 68-km² catchment in the low Arctic of north-western Canada. The model uses a Landsat-derived vegetation classification and a digital elevation model to segregate the basin into snow 'sources' and 'sinks'. The model then relocates snow from sources to sinks and calculates in-transit sublimation loss. The resulting annual snow accumulation in specific landscape types was compared with the result of intensive surveys of snow depth and density. On an annual basis, 28% of annual snowfall sublimated from tundra surfaces whilst 18% was transported to sink areas. Annual blowing snow transport to sink areas amounted to an additional 16% of annual snowfall to shrub-tundra and an additional 182% to drifts. For the catchment, 19.5% of annual snowfall sublimated from blowing snow, 5.8% was transported into the catchment and 86.5% accumulated on the ground. The model overestimated snow accumulation in the catchment by 6%. The application demonstrates that winter precipitation alone is insufficient to calculate snow accumulation and that blowing snow processes and landscape patterns govern the spatial distribution and total accumulation of snow water equivalent over the winter. These processes can be modelled by relatively simple algorithms, and, when distributed by landscape type over the catchment, produce reasonable estimates of snow accumulation and loss in wind-swept regions. (Au)

F, E, H, J
Accumulation; Blowing snow; Evaporation; Mathematical models; Plant distribution; Snow; Snow cover; Snow hydrology; Snow surveys; Snowdrifts; Snowfall; Sublimation; Surface properties; Topography; Tundra ecology; Winds

G0812, G06
Prudhoe Bay region, Alaska; Trail Valley Creek, N.W.T.


Shrub tundra snowmelt   /   Pomeroy, J.W.   Bewley, D.S.   Essery, R.L.H.   Hedstrom, N.R.   Link, T.   Granger, R.J.   Sicart, J.E.   Ellis, C.R.   Janowicz, J.R.
(Special issue : Eastern Snow Conference/Western Snow Conference / Edited by J. Pomeroy, A.G. Klein, and K. Elder. Hydrological processes, v. 20, no. 4, 15 Mar. 2006, p. 923-941, ill.)
References.
ASTIS record 66082.
Languages: English
Web: doi:10.1002/hyp.6124
Libraries: ACU

Observations of land surface and snowpack energetics and mass fluxes were made over arctic shrub tundra of varying canopy height and density using radiometers, eddy covariance flux measurements, and snow mass changes from snow surveys of depth and density. Over several years, snow accumulation in the shrubs was found to be consistently higher than in sparse tundra due to greater retention of snowfall by all shrubs and wind redistribution of snowfall to tall shrubs. Where snow accumulation was highest due to snow redistribution, shrubs often became buried by the end of winter. Three classes of shrub-snow interactions were observed: tall shrubs that were exposed over snow, tall shrubs that were bent over and buried by snow, and short shrubs buried by snow. Tall shrubs buried by snow underwent "spring-up" during melt. Though spring-up was episodic for a single shrub, over an area it was a progressive emergence from early to mid melt of vegetation that dramatically altered the radiative and aerodynamic properties of the surface. Short shrubs were exposed more rapidly once snow depth declined below shrub height, usually near the end of melt. Net radiation increased with increasing shrub due to the decreased reflectance of shortwave radiation overwhelming the increased longwave emission from relatively warm and dark shrubs. Net radiation to snow under shrubs was much smaller than that over shrubs, but was greater than that to snow with minimal shrub exposure, in this case the difference was due to downward longwave radiation from the canopy exceeding the effect of attenuated shortwave transmission through the canopy. Because of reduced turbulent transfer under shrub canopies and minimal water vapour contributions from the bare shrub branches, sublimation fluxes declined with increasing shrub exposure. In contrast, sensible heat fluxes to the shrub surface became more negative and those to the underlying snow surface more positive with increasing shrub exposure, because of relatively warm shrub branches, particularly on clear days. From well-exposed tall shrubs, both a large upward sensible heat flow from shrub to atmosphere and a downward flow that contributed substantially to snowmelt were detected. As a result of radiative and turbulent transfer in shrub canopies, melt rates increased with shrub exposure. However, shrub exposure was not a simple function of shrub height or presence, and the transition to shrub-exposed landscape depended on initial snow depth, shrub height, shrub species and cumulative melt, and this in turn controlled the melt energetics for a particular site. As a result of these complex interactions, observations over several years showed that snowmelt rates were generally, but not always, enhanced under shrub canopies in comparison with sparsely vegetated tundra. (Au)

H, F, E, J
Ablation; Albedo; Blowing snow; Mathematical models; Measurement; Microclimatology; Plant cover; Plant growth; Radiation budgets; Seasonal variations; Shrubs; Snow; Snow hydrology; Snow water equivalent; Snowmelt; Sublimation; Tundra ecology; Water vapour

G0811
Wolf Creek (60 37 15 N, 134 54 45 W) region, Yukon


Studies on snow redistribution by wind and forest, snow-covered area depletion, and frozen soil infiltration in northern and western Canada   /   Pomeroy, J.W.   Gray, D.M.   Marsh, P.
In: Cold region atmospheric and hydrologic studies : the Mackenzie GEWEX experience. Volume 2 : hydrologic processes / Edited by Ming-ko Woo. - New York : Springer, 2008, ch. 5, p. 81-96, ill., maps
References.
ASTIS record 68676.
Languages: English
Web: doi:10.1007/978-3-540-75136-6
Libraries: ACU

Important advances in our understanding of snow and frozen soil processes have been made, especially in regard to the transport and sublimation of blowing snow, interception and sublimation of snow in forest canopies, snow spatial distributions in complex environments, snowmelt in open environments and under forest canopies, advection of energy from bare ground to snow, snowcover depletion during melt, and heat and mass transfer during infiltration to unsaturated frozen mineral soils. These studies, conducted at the Division of Hydrology at the University of Saskatchewan, covered a range of northern environments including the tundra-taiga transition, the cordilleran sub-arctic, the southern boreal forest, and the northern prairie. Results from field research have led to the development and improvement of algorithms related to snow and infiltration processes, which have contributed to hydrologic and atmospheric models in the Mackenzie GEWEX Study. (Au)

F, H, E, A
Ablation; Blowing snow; Boundary layers; Evaporation; Forests; Frozen ground; Heat transmission; Hummocks; Hydrological stations; Hydrology; Land classification; Mapping; Mathematical models; Measurement; Meteorology; Moisture transfer; Peat; Pines; Plant-water relationships; Precipitation (Meteorology); River discharges; Runoff; Satellite photography; Seasonal variations; Snow; Snow loads; Snow surveys; Snow water equivalent; Snowmelt; Snowpatches; Soil temperature; Spatial distribution; Stream flow; Sublimation; Surface properties; Temporal variations; Topography; Treeline; Weather stations; Winds

G0812
Inuvik region, N.W.T.; Mackenzie River region, N.W.T.; Trail Valley Creek region, N.W.T.; Wolf Lake (60 39 40 N, 131 40 30 W) region, Yukon


The influence of mineral earth hummocks on subsurface drainage in the continuous permafrost zone   /   Quinton, W.L.   Marsh, P.
(Permafrost and periglacial processes, v. 9, no. 3, July-Sept. 1998, p. 213-228, ill., maps)
References.
ASTIS record 47553.
Languages: English
Web: doi:10.1002/(SICI)1099-1530(199807/09)9:3<213::AID-PPP285>3.0.CO;2-E
Libraries: ACU

Mineral earth hummocks are one of the most widely distributed forms of patterned ground in the permafrost areas of the world, yet little is known of their hydrological role in the drainage of hillslopes. The impact of earth hummocks on subsurface drainage was studied at three hillslope plots during the snow-free periods of 1993 and 1994 at a small hummock-covered Arctic tundra watershed (Siksik Creek) in north-western Canada. Subsurface drainage occurs preferentially through the unfrozen saturated layer of the inter-hummock area, owing to its relatively high permeability and connected nature. The inter-hummock area is composed of primary channels, oriented in the downslope direction, and secondary channels, obstructed from conducting water directly downslope. Because of their very low hydraulic conductivity, earth hummocks obstruct hillslope drainage. As a result, the spatial distribution of earth hummocks on a hillslope influences the average tortuosity of the individual inter-hummock channels that comprise the hillslope drainage network. The time required for runoff water to reach the streambank increases with increasing tortuosity of inter-hummock channels. Earth hummocks attenuate subsurface flows owing to seepage between the hummocks and the inter-hummock area. Hummocks also displace the water table in the inter-hummock area upward into a zone where the hydraulic conductivity can be orders of magnitude higher. (Au)

A, C, F, E
Drainage; Hummocks; Hydrology; Meteorology; Patterned ground; Periglacial landforms; Runoff; Snowmelt; Soil moisture; Thermokarst; Topography

G0812
Siksik Creek region, N.W.T.; Siksik Creek, N.W.T.


Recent advances toward physically-based runoff modeling of the wetland-dominated central Mackenzie River basin   /   Quinton, W.L.   Hayashi, M.
In: Cold region atmospheric and hydrologic studies : the Mackenzie GEWEX experience. Volume 2 : hydrologic processes / Edited by Ming-ko Woo. - New York : Springer, 2008, ch. 14, p. 257-279, ill., maps
References.
ASTIS record 68675.
Languages: English
Web: doi:10.1007/978-3-540-75136-6
Libraries: ACU

Field studies were initiated in 1999 at Scotty Creek in central Mackenzie River Basin to improve understanding and model-representation of the major water flux and storage processes within a wetland-dominated zone of the discontinuous permafrost region. Four main topics were covered: (1) the major peatland types and their influence on basin runoff, (2) the physical processes governing runoff generation, (3) how runoff processes observed at the hillslope scale relate to basin-scale runoff, and (4) the water balance of Scotty Creek and its adjacent basins. A conceptual model of runoff generation was developed that recognizes distinct hydrologic roles among the major peatland types of flat bog, channel fen and peat plateau. This model contributes to resolving some of the difficult issues in the hydrologic modeling in this region, especially in relation to the storage and routing functions of wetlands-dominated basins underlain by discontinuous permafrost. (Au)

F, H, E, A, C
Active layer; Bogs; Climate change; Cores; Drainage; Evaporation; Frozen ground; Groundwater; Hummocks; Hydrological stations; Hydrology; Lakes; Mathematical models; Measurement; Meteorology; Peat; Permafrost; Plant cover; Plant-soil relationships; Plants (Biology); Precipitation (Meteorology); River discharges; Runoff; Satellite photography; Seasonal variations; Slopes; Snow surveys; Snowmelt; Soil moisture; Soil profiles; Soil texture; Spatial distribution; Surface properties; Temporal variations; Topography; Treeline; Unfrozen water content of frozen ground; Weather stations; Wetlands

G0812
Birch River region, N.W.T.; Blackstone River region, N.W.T.; Fort Simpson region, N.W.T.; Jean Marie River region, N.W.T.; Mackenzie River region, N.W.T.; Scotty Creek region, N.W.T.; Scotty Creek, N.W.T.


Impact of the Canadian land surface scheme on monthly ensemble predictions of water and energy budgets over the Mackenzie River basin   /   Radeva, E.   Ritchie, H.
(Atmosphere-ocean, v. 39, no. 2, June 2001, p. 71-88, ill., maps)
References.
ASTIS record 50429.
Languages: English
Libraries: ACU

As part of the Mackenzie GEWEX Study (MAGS), Canadian global spectral forecast model (SEF) monthly simulations of surface water and energy fluxes averaged over the Mackenzie River basin are examined. We study the impact of the more sophisticated Canadian Land-Surface Scheme (CLASS) on the predictability of the fluxes, using the operational configuration of the global model with the force-restore land-surface scheme as a baseline for comparison. The model, connected successively to the current operational force-restore land surface scheme and to CLASS, generates nine-member ensemble simulations of one month duration from analyses perturbed with the Monte-Carlo method, for spring, summer, fall and winter cases. The perturbations are comparable in magnitude to observational errors. The flux predictability is measured by the degree to which the individual forecasts in the ensembles vary from one another. The mean of the ensemble forecasts is compared with monthly accumulations of surface energy and water fields constructed from 12-hour forecasts of the operational Regional Finite Element (RFE) model as well as with satellite-derived observations of precipitation. We found that, overall, the replacement of the force-restore scheme with CLASS in the Canadian Meteorological Centre (CMC) global forecasting system has a beneficial effect on the predicted MAGS energy and water budgets. While their sensitivity to initial conditions increases only slightly, the budgets, forecast with CLASS, compare better with their counterparts constructed from the short-term predictions of the CMC regional forecasting system than the output of the model coupled with the operational force-restore scheme. (Au)

F, E, C
Energy budgets; Evaporation; Forecasting; Heat budgets; Hydrology; Mathematical models; Meteorology; Precipitation (Meteorology); Remote sensing; Rivers; Soil moisture; Solar radiation; Temperature; Weather forecasting

G0812
Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; Mississippi River, United States


Effects of climate change on the freshwaters of Arctic and Subarctic North America   /   Rouse, W.R.   Douglas, M.S.V.   Hecky, R.E.   Hershey, A.E.   Kling, G.W.   Lesack, L.   Marsh, P.   McDonald, M.   Nicholson, B.J.   Roulet, N.T.   Smol, J.P.
(Freshwater ecosystems and climate change in North America / Edited by C.E. Cushing. Hydrological processes, v. 11, no. 8, 30 June 1997, p. 873-902, ill., maps)
References.
ASTIS record 60827.
Languages: English
Web: doi:10.1002/(SICI)1099-1085(19970630)11:8<873::AID-HYP510>3.0.CO;2-6
Libraries: ACU

Region 2 comprises arctic and subarctic North America and is underlain by continuous or discontinuous permafrost. Its freshwater systems are dominated by a low energy environment and cold region processes. Central northern areas are almost totally influenced by arctic air masses while Pacific air becomes more prominent in the west, Atlantic air in the east and southern air masses at the lower latitudes. Air mass changes will play an important role in precipitation changes associated with climate warming. The snow season in the region is prolonged resulting in long-term storage of water so that the spring flood is often the major hydrological event of the year, even though, annual rainfall usually exceeds annual snowfall. The unique character of ponds and lakes is a result of the long frozen period, which affects nutrient status and gas exchange during the cold season and during thaw. GCM models are in close agreement for this region and predict temperature increases as large as 4°C in summer and 9°C in winter for a 2 × CO2 scenario. Palaeoclimate indicators support the probability that substantial temperature increases have occurred previously during the Holocene. The historical record indicates a temperature increase of > 1°C in parts of the region during the last century. GCM predictions of precipitation change indicate an increase, but there is little agreement amongst the various models on regional disposition or magnitude. Precipitation change is as important as temperature change in determining the water balance. The water balance is critical to every aspect of hydrology and limnology in the far north. Permafrost close to the surface plays a major role in freshwater systems because it often maintains lakes and wetlands above an impermeable frost table, which limits the water storage capabilities of the subsurface. Thawing associated with climate change would, particularly in areas of massive ice, stimulate landscape changes, which can affect every aspect of the environment. The normal spring flooding of ice-jammed north-flowing rivers, such as the Mackenzie, is a major event, which renews the water supply of lakes in delta regions and which determines the availability of habitat for aquatic organisms. Climate warming or river damming and diversion would probably lead to the complete drying of many delta lakes. Climate warming would also change the characteristics of ponds that presently freeze to the bottom and result in fundamental changes in their limnological characteristics. At present, the food chain is rather simple usually culminating in lake trout or arctic char. A lengthening of the growing season and warmer water temperature would affect the chemical, mineral and nutrient status of lakes and most likely have deleterious effects on the food chain. Peatlands are extensive in region 2. They would move northwards at their southern boundaries, and, with sustained drying, many would change form or become inactive. Extensive wetlands and peatlands are an important component of the global carbon budget, and warmer and drier conditions would most likely change them from a sink to a source for atmospheric carbon. There is some evidence that this may be occurring already. Region 2 is very vulnerable to global warming. Its freshwater systems are probably the least studied and most poorly understood in North America. There are clear needs to improve our current knowledge of temperature and precipitation patterns; to model the thermal behaviour of wetlands, lakes and rivers; to understand better the interrelationships of cold region rivers with their basins; to begin studies on the very large lakes in the region; to obtain a firm grasp of the role of northern peatlands in the global carbon cycle; and to link the terrestrial water balance to the thermal and hydrological regime of the polar sea. Overall, there is a strong need for basic research and long-term monitoring. (Au)

F, E, J, C, I, H, G, B
Atmospheric humidity; Atmospheric temperature; Bioclimatology; Biological productivity; Breakup; Carbon cycling; Climate change; Drainage; Effects of climate on ice; Effects of climate on permafrost; Effects of climate on plants; Effects of climate on snow; Environmental impacts; Erosion; Evaporation; Fishes; Floods; Food chain; Formation; Fresh-water ecology; Fresh-water fauna; Fresh-water flora; Frozen ground; Groundwater; Growing season; Hydrology; Ice jams; Lake ice; Lakes; Mathematical models; Mosses; Palaeoclimatology; Peat; Permafrost; Plant distribution; Rain; Recent epoch; River discharges; River ice; Rivers; Roots; Runoff; Seasonal variations; Snow; Snowmelt; Soil moisture; Soil temperature; Solar radiation; Spatial distribution; Stream flow; Sublimation; Suspended solids; Temperature; Thawing; Thermal regimes; Thickness; Tundra ponds; Water level; Wetlands; Wildlife habitat; Winds

G081, G0812, G06
Alaska; Canadian Arctic; Mackenzie Delta, N.W.T.; Mackenzie River region, N.W.T.


The annual carbon budget for fen and forest in a wetland at Arctic treeline   /   Rouse, W.R.   Bello, R.L.   D'Souza, A.   Griffis, T.J.   Lafleur, P.M.
(Circumpolar Ecosystems 2000. Arctic, v. 55, no. 3, Sept. 2002, p. 229-237, ill., 2 maps)
References.
ASTIS record 50092.
Languages: English
Web: http://pubs.aina.ucalgary.ca/arctic/Arctic55-3-229.pdf
Web: doi:10.14430/arctic707
Libraries: ACU

Three separate research efforts conducted in the same wetland-peatland system in the northern Hudson Bay Lowland near the town of Churchill, Manitoba, allow a comparison of two carbon budget estimates, one derived from long-term growth rates of organic soil and the other based on shorter-term flux measurements. For a tundra fen and an open subarctic forest, calculations of organic soil accumulation or loss over the last half-century indicate that while the fen on average has lost small amounts of carbon from the ecosystem, the adjacent forest has gained larger amounts of atmospheric carbon dioxide. These longer-term data are supported by shorter-term flux measurements and estimates, which also show carbon loss by the fen and carbon uptake by the forest. The shorter-term data indicate that the fen's carbon loss is largely attributable to exceptionally dry years, especially if they are warm. The forest may gain carbon at an increased rate as it matures and during warm growing seasons. Also, the changes in relief of the dynamic hummock-hollow landscape in the fen may inhibit photosynthesis. (Au)

H, F, J, E, C
Bioclimatology; Carbon; Carbon cycling; Climate change; Forest ecology; Forests; Hummocks; Hydrology; Peat; Soils; Wetlands

G0824
Churchill region, Manitoba


An investigation of the thermal and energy balance regimes of Great Slave and Great Bear lakes   /   Rouse, W.R.   Blanken, P.D.   Bussières, N.   Oswald, C.J.   Schertzer, W.M.   Walker, A.E.
(Journal of hydrometeorology, v. 9, no. 6, Dec. 2008, p.1318-1333, ill., maps)
References.
ASTIS record 68682.
Languages: English
Web: doi:10.1175/2008JHM977.1
Libraries: ACU

Great Slave Lake and Great Bear Lake have large surface areas, water volumes, and high latitudinal positions; are cold and deep; and are subject to short daylight periods in winter and long ones in summer. They are dissimilar hydrologically. Great Slave Lake is part of the Mackenzie Basin flowthrough system. Great Bear Lake is hydrologically isolated in its own relatively small drainage basin and all of its inflow and outflow derive from its immediate watershed. Great Slave Lake's outflow into the Mackenzie River is more than 8 times that from Great Bear Lake. Input from the south via the Slave River provides 82% of this outflow volume. These hydrological differences exert pronounced effects on the thermodynamics, hydrodynamics, and surface climates of each lake. The quantitative results in this study are based on limited datasets from different years that are normalized to allow comparison between the two lakes. They indicate that both lakes have regional annual air temperatures within 2°C of one another, but Great Slave Lake exhibits a much longer open-water period with higher temperatures than Great Bear Lake. During the period when the lakes are warming, each lake exerts a substantial overlake atmospheric cooling, and in the period when the lakes are cooling, each exerts a strong overlake warming. This local cooling and warming cycle is greatest over Great Bear Lake. Temperature and humidity inversions are frequent early in the lake-warming season and very strong lapse gradients occur late in the lake-cooling season. Annually, for both lakes, early ice breakup is matched with late freeze-up. Conversely, late breakup is matched with early freeze-up. The magnitudes of midlake latent heat fluxes (evaporation) and sensible heat fluxes from Great Slave Lake are substantially larger than those from Great Bear Lake during their respective open-water periods. The hypothesis that because they are both large and deep, and are located in high latitudes, Great Slave Lake and Great Bear Lake will exhibit similar surface and near-surface climates that are typical of large lakes in the high latitudes proves invalid because their different hydrological systems impose very different thermodynamic regimes on the two lakes. Additionally, such an extensive north-flowing river system as the Mackenzie is subjected to latitudinally variable meteorological regimes that will differentially influence the hydrology and energy balance of these large lakes. Great Slave Lake is very responsive to climatic variability because of the relation between lake ice and absorbed solar radiation in the high sun season and we expect that Great Bear Lake will be affected in a similar fashion. (Au)

F, E, G
Atmospheric humidity; Atmospheric pressure; Atmospheric temperature; Bathymetry; Breakup; Energy budgets; Evaporation; Formation; Heat transmission; Hydrology; Lake ice; Lake stratification; Lake-atmosphere interaction; Lakes; Mathematical models; Measurement; Meteorology; River discharges; Seasonal variations; Snow cover; Solar radiation; Surface temperature; Temperature; Temporal variations; Thermal properties; Thermodynamics; Thickness; Water level; Watersheds; Weather forecasting

G0812
Great Bear Lake region, N.W.T.; Great Slave Lake region, N.W.T.; Mackenzie River region, N.W.T.


Quantifying the fundamental physical responses of Great Bear Lake to climate variability and change : measurement and modelling of temperature and fluxes   /   Schertzer, W.   Rouse, W.   Blanken, P.   Lam, D.   Yerubandi, R.R.   Swayne, D.   Carmack, E.   Gyakum, J.
In: 2008 Congress, Canadian Meteorological and Oceanographic Society, May 25-29, 2008, Kelowna, B.C. : water, weather, and climate : science informing decisions = Congrés 2008, la Société canadienne de météorologie et d'océanographie, 25-29 mai, 2008, Kelowna, C.-B. : eau, météo, et climat : la science comme outil de décision. - Ottawa : CMOS, 2008, [1] p.
Abstract of an oral presentation in Session 1C1.4, ID:2267.
Session 1C1: IPY, part 2 of 4: Hydrology.
Indexed a PDF file from the Web.
ASTIS record 76129.
Languages: English
Web: http://www.cmos.ca/CongressAbstracts/cong4208.pdf
Libraries: ACU

This multi-year IPY investigation is focused on: (a) understanding the current conditions on Great Bear Lake (GBL), (b) quantifying the response to climatic variability and, (c) projecting potential impacts of climate change. In an earlier study, Meyer et al. (1994) applied a 1-D temperature model with a GFDL climate scenario to GBL. They suggested that under climate warming, ice cover would be reduced from 82% to 65% of the year. Increased convective mixing in the lake during spring and autumn could alter its monomictic state to become dimictic with hydrophysical features similar to temperate lakes. The major limitation of the Meyer et al. (1994) analysis was the necessity to use climate data from Aklavik - nearly 650 km from GBL. The study drew attention to the paucity of data and knowledge on the fundamental physical responses of this northern lake to climate variability and change. In 2004-05, Rouse et al. conducted observations within the Keith Arm of GBL as a contribution to GEWEX-MAGS. The investigation quantified the magnitude and inter-annual variability of the surface heat flux, mass exchange and lake temperature adding knowledge to the baseline conditions. The study suggested that Great Bear Lake is very responsive to climatic variability, being influenced by the length of the ice free season and absorbed solar radiation. The current IPY study is an extension of the previous research. It will employ direct in situ intensive time-series of meteorological, radiation and limnological observations to provide the necessary spatial representation to describe the baseline physical conditions and for development and verification of thermal/hydrodynamic models to be applied to understand the impact of climate on this resource. This talk presents important results from past research and describes the multi-year field program, the challenging field deployments and modelling to be applied during the IPY investigation. (Au)

F, E, G
Climate change; Environmental impacts; Heat transmission; Ice cover; Lake ice; Lake stratification; Lake-atmosphere interaction; Lakes; Mathematical models; Meteorology; Seasonal variations; Snow cover; Solar radiation; Spatial distribution; Temperature; Temporal variations; Thermal regimes

G0812
Great Bear Lake region, N.W.T.


Changes to the distribution of monthly and annual runoff in the Mackenzie Basin under climate change using a modified square grid approach   /   Soulis, E.D.   Solomon, S.I.   Lee, M.   Kouwen, N.
In: Mackenzie Basin Impact Study (MBIS), interim report #2 : proceedings of the Sixth Biennial AES/DIAND Meeting on Northern Climate & Mid Study Workshop of the Mackenize Basin Impact Study, Yellowknife, Northwest Territories, April 10-14, 1994 / Edited by J. Cohen. - Downsview, Ont. : Environment Canada, 1994, p. 197-209, ill., 1 map
ASTIS record 36869.
Languages: English
Libraries: ACU

The climate change scenarios considered by MBIS all have water resources implications. They predict changes in precipitation and temperature patterns over the Mackenzie Basin that will alter local water balances and have an impact on water levels in lakes and wetlands. These differences will ultimately have an effect on flows in the Mackenzie River itself. This paper presents preliminary estimates of how monthly runoff will vary under the CCC, GFDL and Composite scenarios. These results were produced as part of the first phase of a three phase project. Subsequent phases are planned as part of Canadian GEWEX Science Plan. These will involve more detailed streamflow models and will include validation studies to quantify uncertainty in the results. ... (Au)

E, F, N
Atmospheric temperature; Climate change; Lakes; Mathematical models; Precipitation (Meteorology); Runoff; Stream flow; Water level; Water resources

G0812
Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.


The effect of storage on runoff from a headwater Subarctic shield basin   /   Spence, C.
(Arctic, v. 53, no. 3, Sept. 2000, p. 237-247, ill., map)
References.
ASTIS record 46995.
Languages: English
Web: http://pubs.aina.ucalgary.ca/arctic/Arctic53-3-237.pdf
Web: doi:10.14430/arctic855
Libraries: ACU

Canadian Shield runoff production processes have been investigated, but research is needed beyond the hillslope scale to determine the influences on the volume and timing of runoff from headwater basins to higher-order streams. Such research will permit an understanding of the magnitude of climate change impacts at the watershed scale, where changes in the hydrologic regime are felt most by water resource users. To this end, water budget terms were measured over different portions of a headwater lake basin north of Yellowknife, Northwest Territories, during the spring snowmelt of 1998 to determine the relative importance of each component as water moved through the basin. Evaporation made up 16% and runoff 70% of the snowmelt from upland areas. Upland ponding of water during the melt increased the evaporative loss. Headwater lake storage deficits are very important in the timing and volume of runoff that is transmitted downstream: 53% of basin meltwater went to meeting the storage deficit in the lake so that only 7% of the meltwater was routed out of the basin. These results imply that topology of shield headwater basins, notably the location of lakes and antecedent water levels in lakes, are important in determining the runoff response. As storage deficits in surface waters will cause changes over space in runoff response and timing, it may be inappropriate to consider the snowpack or rainfall volume in isolation when forecasting runoff volume. These results are important for water management and hydrological modeling applications of northern shield basins. (Au)

F, E
Climate change; Energy budgets; Evaporation; Hydrography; Lakes; Management; Runoff; Snowmelt; Water level; Water resources; Watershed management

G0812
Yellowknife region, N.W.T.; Yellowknife River, N.W.T.


Towards understanding water and energy processes within the Mackenzie River basin   /   Stewart, R.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 91-94)
References.
A French version of this paper, on p. 95-99, follows the English version under title, "Un pas vers la compréhension des processus hydrologiques et énergétiques dans le bassin du fleuve Mackenzie".
ASTIS record 51869.
Languages: English
Web: doi:10.3137/ao.400201
Libraries: ACU

Canada has one of the largest amounts of fresh water of any country in the world. This resource is, however, subject to large fluctuations due to natural climatic variations (see, for example, Shabbar et al., 1997) and there are concerns about how anthropogenic forcing may alter the Canadian climate. It is critical that approaches be developed to assess our water resources within the context of the overall climate system. This is best accomplished through Canadian efforts linked with international ones. The Global Energy and Water Cycle Experiment (GEWEX) is such an international effort. It was developed by the World Climate Research Programme (WCRP) as a coordinated group of activities aimed at improving our understanding and prediction of the role that the water cycle plays in the climate system. Such improvements are crucial if we are to predict the varying natural climate system and its sensitivity to anthropogenic effects (Chahine, 1992). The strategy being followed within GEWEX to address water availability is first to tackle water and energy issues regionally over large continental regions and then to apply this globally. The water budgets of such large regions should be less sensitive to random errors in the observed and modelled fields. As well, such regions cover significant fractions of continental land masses so that scaling-up the required subsurface, surface, and atmospheric advancements to global application should be easier. Realizing these global goals will require that GEWEX make scientific advances in several areas. The overarching issue is concerned with the better understanding of water and energy processes that are operating over different land areas. Contributing issues include addressing the relative influence of large-scale and local controls on precipitation as well as the feedback mechanisms affecting wet and dry periods. In light of these considerations, the focus of much of Canada's contribution to GEWEX is the Mackenzie River basin (Stewart et al., 1998). This effort is referred to as the Mackenzie GEWEX Study (MAGS) and its objectives are to: understand and model the high latitude water and energy cycles that play roles in the climate system; and improve our ability to assess the changes to Canada's water resources that arise from climate variability and anthropogenic climate change. ... One way of addressing water cycle issues of a particular region such as the Mackenzie River basin is to examine it during periods of extremes. How does a system behave during periods when it is 'at the edge'? This is an important part of the MAGS strategy (Stewart et al., 1998). Many kinds of extremes can be examined since this region experiences large variations in temperature, precipitation and discharge. In this special issue, the focus is on the 1994/95 water year when the discharge from the Mackenzie River into the Arctic Ocean was anomalously low, probably the lowest on record. The discharge was equivalent to 135 mm of precipitation falling over the basin, far lower than the average of 175 mm. It is critical to understand the factors that contributed to this anomaly. There are eleven scientific articles comprising this special issue. ... Each article makes an important scientific contribution and the last article attempts to bring these together into an overall synthesis. (Au)

F, E, D, N, J, G
Breakup; Climate change; Energy budgets; Hydrology; Ocean-atmosphere interaction; Pollution; River discharges; River ice; Temporal variations; Water resources; Watersheds

G0812
Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.


Un pas vers la compréhension des processus hydrologiques et énergétiques dans le bassin du fleuve Mackenzie   /   Stewart, R.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 95-99)
References.
An English version of this paper precedes the French version on p. 91-94, under title, "Towards understanding water and energy processes within the Mackenzie River basin".
ASTIS record 51870.
Languages: French
Web: doi:10.3137/ao.400201f
Libraries: ACU

Le Canada possède quelques-unes des plus grandes réserves d'eau douce au monde. Cependant, ces réserves peuvent fluctuer considérablement en raison des variations naturelles du climat (voir, par exemple, Shabbar et al., 1997), et on craint de plus en plus que le forçage anthropique puisse modifier le climat du Canada. Il est essentiel d'élaborer des stratégies qui permettent d'évaluer nos ressources hydriques dans le contexte du système climatique global. Pour ce faire, il s'agit de lier les efforts canadiens aux initiatives internationales. L'Expérience mondiale sur les cycles de l'énergie et de l'eau (GEWEX) est une de ces initiatives internationales. Élaborée dans le cadre du Programme mondial de recherches sur le climat (PMRC), elle consiste en un groupe d'activités coordonnées dont le but est d'améliorer la compréhension et la prévision du rôle que joue le cycle de l'eau dans le système climatique. Cette amélioration est essentielle si nous voulons prévoir les variations du système climatique naturel et sa sensibilité aux effets anthropiques (Chahine, 1992). La stratégie adoptée dans le cadre de GEWEX pour examiner la disponibilité de l'eau consiste d'abord à s'attaquer aux questions relatives à l'eau et à l'énergie à une échelle régionale sur de vastes étendues continentales, puis à appliquer les résultats à une échelle globale. En principe, les bilans hydriques de régions aussi vastes devraient être moins sensibles aux erreurs aléatoires dans les champs observés et modélisés. De plus, ces régions couvrent des portions significatives des masses continentales, ce qui devrait faciliter la mise à l'échelle globale des résultats relatifs à la subsurface, à la surface et à l'atmosphère. Pour atteindre ces objectifs mondiaux, GEWEX devra réaliser des progrès scientifiques dans plusieurs domaines. La question primordiale consiste à mieux comprendre les processus hydrologiques et énergétiques jouant dans divers territoires. D'autres questions portent sur l'influence relative des facteurs régionaux et locaux régissant la précipitation ainsi que les mécanismes de rétroaction en jeu durant les périodes de précipitations et les périodes sèches. Compte tenu de ces questions, la contribution du Canada à GEWEX est largement centrée sur le bassin du fleuve Mackenzie (Stewart et al., 1998). Cette initiative, baptisée «Étude GEWEX du Mackenzie» (MAGS), a pour objectifs ullet de comprendre et de modéliser les cycles de l'énergie et de l'eau qui ont un rôle à jouer dans les régions froides; et ullet d'améliorer notre capacité d'évaluer les changements survenus aux ressources hydriques du Canada qui sont attribuables à la variabilité du climat et au changement climatique d'origine anthropique. L'étude du bassin du fleuve Mackenzie se rattache à d'autres études de bassins de grands cours d'eau entreprises sous l'égide du groupe d'experts en hydrométéorologie de GEWEX (voir, par exemple, Roads et al., 2002), notamment l'étude du fleuve Mississippi à écoulement vers le sud (GAPP, décrite par Lawford, 1999), l'étude de l'Amazone (LBA, décrite par Nobre et al., 1996), l'étude de la région de la mer Baltique (BALTEX, décrite par Raschke et al., 2001) et l'étude de la région de mousson d'Asie (GAME, décrite par GAME International Science Panel, 1998). D'autres études sont en voie d'élaboration pour l'Australie et l'Afrique. L'accent mis par le Canada sur un cours d'eau septentrional complète ces études de bassins. Une stratégie pour étudier le cycle de l'eau dans une région donnée comme le bassin du fleuve Mackenzie consiste à examiner la région au cours de périodes de conditions extrêmes. Comment se comporte un système pendant de telles périodes? Voilà une partie importante de la stratégie de l'étude MAGS (Stewart et al., 1998). Il est possible d'examiner de nombreux types de conditions extrêmes, car la région connaît des variations importantes au niveau de la température, des précipitations et du débit. Ce numéro spécial se concentre sur l'année hydrologique 1994-1995, année pendant laquelle le débit du fleuve Mackenzie dans l'océan Arctique a été anomalement faible, vraisemblablement le plus faible enregistré. Le débit était équivalent à 135 mm de précipitation tombant dans le bassin, ce qui est beaucoup moins élevé que la moyenne de 175 mm. Il est indispensable de comprendre les facteurs ayant contribué à cette anomalie. Ce numéro spécial comporte onze articles qui sont décrits brièvement ci-dessous. En général, les articles sont présentés «en cascade», allant des études à grande échelle de l'atmosphère aux études à petite échelle de la surface du sol. Chaque article apporte une contribution scientifique importante, et le dernier article fait une synthèse globale de l'ensemble. (Au)

F, E, D, N, J
Breakup; Climate change; Energy budgets; Hydrology; Mathematical models; Ocean-atmosphere interaction; Pollution; River discharges; River ice; Temporal variations; Water resources; Watersheds

G0812
Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.


Hydrometeorological features of the Mackenzie basin climate system during the 1994/95 water year : a period of record low discharge   /   Stewart, R.E.   Bussières, N.   Cao, Z.   Cho, H.R.   Hudak, D.R.   Kochtubajda, B.   Leighton, H.   Louie, P.Y.T.   Mackay, M.D.   Marsh, P.   Strong, G.S.   Szeto, K.K.   Burford, J.E.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 257-278, ill., maps)
References.
ASTIS record 51881.
Languages: English
Web: doi:10.3137/ao.400212
Libraries: ACU

The phenomena that occurred within and in the vicinity of the Mackenzie basin climate system during the 1994/95 water year are the focus of this study. This water year was characterized by a record low discharge and by a very early discharge into the Arctic Ocean. The low discharge arose because the efficiency with which the record-low large-scale moisture convergence over the Mackenzie basin was converted into discharge was also the lowest on record. This low efficiency occurred as a consequence of many atmospheric, surface and hydrological processes and feedbacks occurring during this period. The dry surface conditions that had developed just prior to the start of the water year were also a contributing factor. It is evident through the comprehensive examination of the overall climate system of this basin that many strongly coupled processes were occurring. Our models are able to account for some of these, but more research is needed to address a number of them. (Au)

F, E
Atmospheric circulation; Atmospheric electricity; Atmospheric humidity; Atmospheric pressure; Atmospheric temperature; Blowing snow; Clouds; Evaporation; Forest fires; Hydrology; Lakes; Mathematical models; Meteorology; Ocean-atmosphere interaction; Precipitation (Meteorology); River discharges; Rivers; Snow cover; Snowmelt; Storms; Water level; Water vapour; Winds

G0812, G0821, G0811, G03, G07, G05, G0822, G0823
Alberta; Arctic Ocean; Athabasca, Lake, Alberta/Saskatchewan; British Columbia; Canadian Beaufort Sea; Great Bear Lake, N.W.T.; Great Slave Lake, N.W.T.; Mackenzie Delta, N.W.T.; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; N.W.T.; North Pacific Ocean; Saskatchewan; Yukon


Closing the Mackenzie basin water budget, water years 1994/95 to 1996/97   /   Strong, G.S.   Proctor, B.   Wang, M.   Soulis, E.D.   Smith, C.D.   Seglenieks, F.   Snelgrove, K.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 113-124, ill., 1 map)
References.
ASTIS record 51872.
Languages: English
Web: doi:10.3137/ao.400203
Libraries: ACU

A particularly elusive science objective for the Mackenzie Global Energy and Water Cycle Experiment (GEWEX) Study (MAGS) has been to close the atmospheric moisture budget and rationalize it against the surface water budget at annual or even monthly timescales. The task, while not difficult in principle, is complicated by two factors. First is the importance of basin snow-cover, soil and water-body storage in the surface water budget. Month-to-month changes in these components are frequently greater than the atmospheric flux terms, for example, during spring snowmelt. Furthermore, there is approximately a six-week lag before local changes are evident in the discharge at the mouth of the basin. Second, the coarse resolution of all of the supporting data may add significant systematic errors. For example, the two radiosonde soundings per day available to the project are unlikely to account adequately for all the moisture generated locally through evapotranspiration during the summer convective season. This analysis will directly address these two main issues by applying hydrologic and atmospheric computations to assess the storage question, and by using additional soundings at a single site to sample the diurnal signature in atmospheric moisture caused by evapotranspiration. Resulting modifications to the atmospheric moisture and surface water budgets then allow near closure of the MAGS monthly water budget within acceptable error limits. (Au)

F, E, C
Atmospheric humidity; Climate change; Diurnal variations; Energy budgets; Evaporation; Hydrology; Mass balance; Mathematical models; Precipitation (Meteorology); River discharges; Seasonal variations; Snow; Snowmelt; Soil moisture; Stream flow; Water vapour

G0812
Fort Smith, N.W.T.; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.


Moisture recycling over the Mackenzie basin   /   Szeto, K.K.
(MAGS : Mackenzie Étude GEWEX Study. Atmosphere-ocean, v. 40, no. 2, June 2002, p. 181-197, ill., maps)
References.
ASTIS record 51876.
Languages: English
Web: doi:10.3137/ao.400207
Libraries: ACU

Moisture recycling over the Mackenzie basin is investigated by estimating the precipitation recycling ratio (the ratio of precipitation derived from local evaporation to the total precipitation within the basin) for the region with the National Centers for Environmental Prediction (NCEP) reanalysis dataset and the Meteorological Service of Canada (MSC) precipitation climatology. The results suggest that recycling is very active over the region during the warm season (April - August) and extremely inactive during the cold season. The annual recycling ratio estimated for the basin is about 0.25, which is close to that estimated by others for the Mississippi and Amazon basins despite the lower annual evapotranspiration over the Mackenzie basin. The high recycling ratios and the recycling patterns estimated for the basin during the warm season are found to be consequences of the unique topographical and climatic settings characterizing the region. Analysis of conditions during the years having anomalous spring and summer precipitation suggests that the large-scale atmospheric setting could act in concert with the basin's unique topographic and surface characteristics to increase or to decrease precipitation and its recycling over the basin, depending on whether the basin is under the influence of a persistent large-scale low or a high pressure system. In the former case, much of the recycled precipitation would fall over the north-western parts of the basin where the runoff ratios are relatively high, and thus enhance the summer discharge from the basin. When the basin is under the influence of a persistent high pressure system, much of the recycled precipitation would fall over the southern part of the basin where the runoff ratios are relatively low, and thus reduce the discharge from the basin. It is suggested that this latter effect might have contributed to the record low summer discharge from the basin during 1995. (Au)

E, F
Atmospheric circulation; Atmospheric pressure; Evaporation; Hydrology; Mathematical models; Measurement; Meteorology; Precipitation (Meteorology); River discharges; Runoff; Spatial distribution; Synoptic climatology

G0812, G082, G0811
Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.


Northern tales : a synthesis of MAGS atmospheric and hydrometeorological research   /   Szeto, K.K.   Stewart, R.E.   Yau, M.K.   Gyakum, J.
(Bulletin of the American Meteorological Society, v. 88, no. 9, Sept. 2007, p.1411-1425, ill., maps)
References.
ASTIS record 64893.
Languages: English
Web: doi:10.1175/BAMS-88-9-1411
Libraries: ACU

The Mackenzie Global Energy and Water Cycle Experiment (GEWEX) Study (MAGS) is one of the continental-scale experiments approved specifically by GEWEX to better understand and model water and energy cycling at high latitudes. The project has gone through two phases since its inception in 1994 and conclusion in December 2005. Many scientific results have been achieved through MAGS research to advance our understanding of the Mackenzie River basin climate system. This article is a synthesis of its atmospheric research achievements through an integrative description of the basin's climate system, along with highlights of MAGS research that has advanced our knowledge and understanding of various key aspects of the system. In particular, the significance of MAGS research is discussed in the context of how it contributes to enhancing knowledge of the basin's hydroclimate with focuses on i) the large-scale atmospheric processes that control the transport of water and energy into the basin, and ii) the interactions of the large-scale atmospheric flows with physical features of the basin's environment in affecting the weather and climate of the basin. (Au)

E, F, A
Atmospheric circulation; Atmospheric humidity; Atmospheric pressure; Atmospheric temperature; Blowing snow; Climate change; Clouds; Diurnal variations; Energy budgets; Evaporation; Hydrology; Lakes; Mathematical models; Mountains; Precipitation (Meteorology); Radiation budgets; Rivers; Runoff; Seasonal variations; Snow cover; Snowmelt; Solar radiation; Spatial distribution; Storms; Sublimation; Synoptic climatology; Temporal variations; Thermal regimes; Topography; Water vapour

G0812, G0811, G0821, G0822, G0823
Alberta; British Columbia; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; N.W.T.; Saskatchewan, Northern; Yukon


Sensitivity of regional snowpack simulations over eastern Canada to model configuration and boundary conditions   /   Verseghy, D.
In: International Polar Year Oslo Science Conference, 2010, 8-12 June. - [Oslo : Research Council of Norway, 2010], presentation no. EM9.2-3.1, [1] p.
Abstract of an oral presentation, taken from the USB flash drive distributed at the conference.
ASTIS record 71403.
Languages: English

The Canadian initiative "Variability and Change in the Canadian Cryosphere" is a contribution to the International Polar Year project "State and Fate of the Polar Cryosphere". One subtheme of the project involves offline testing of the cryospheric aspects of the Canadian Land Surface Scheme, CLASS. The testing is being carried out over a domain centred on the province of Quebec in eastern Canada, at a resolution of ¼°, The modelling time period incorporates one spin-up year (1991-1992), followed by six simulation years (1992-1998). This includes the warm El Nino winter of 1997-98 (the lowest snow year on record in Quebec). Atmospheric forcing data have been obtained from ERA-40 reanalyses, scaled down in space and time using the Environment Canada GEM model as the interpolator. The background soil and vegetation data used were compiled over North America at 1 km resolution for the Mackenzie GEWEX study. Validation data consist of CANGRID monthly air temperatures, NOAA daily snow cover data, a daily snow depth and SWE reconstruction by Brown et al. (2003), and bimonthly SWE observations over Quebec from snow courses. The focus of this presentation will be the evaluation of the CLASS snow simulation over the modeling domain, and an investigation of the sensitivity of the snow simulation to various land surface characteristics and model parametrizations. Keywords: snow modelling, regional climate, CLASS. (Au)

F, E, C, H, J
Atmospheric temperature; Climatology; Energy budgets; Heat transmission; Land classification; Mathematical models; Plant cover; Snow; Snow cover; Snowfall; Soil moisture; Soil temperature; Surface properties; Taiga ecology; Temporal variations

G0826
Québec


Snow-cover variations over the Mackenzie River basin, Canada, derived from SSM/I passive-microwave satellite data   /   Walker, A.E.   Silis, A.
(Papers from the International Symposium on Remote Sensing in Glaciology, held in Maryland, U.S.A., 4-8 June 2001 / Edited by J.-G. Winter and R. Solberg. Annals of glaciology, v. 34, 2002, p. 8-14, maps)
References.
ASTIS record 51952.
Languages: English
Web: doi:10.3189/172756402781817680
Libraries: ACU

The Mackenzie GEWEX Study (MAGS) is a Canadian investigation that has the objective of understanding and modelling the water and energy cycles and their roles in the climate system in the high-latitude Mackenzie River basin, including assessing potential changes due to climate variability and change. The Climate Research Branch (CRB) of the Meteorological Service of Canada has investigated snow-cover variations over the MAGS region using snow water equivalent (SWE) datasets derived from Special Sensor Microwave/Imager (SSM/I) passive-microwave satellite data for the winter seasons 1988-98. The SWE datasets were derived using four CRB algorithms for prairie, coniferous-forest, deciduous-forest and sparse-forest land-cover types and then evaluated against available in situ SWE measurements for MAGS sub-basins. Overall, the SWE algorithms produce reliable estimates (within 10-20 mm of in situ SWE measurements) for the validated part of the MAGS region, although some areas exhibit underestimations of >30 mm, which may be due to the presence of a high density of lakes or a decreased microwave sensitivity to high-SWE conditions (>100 mm). A time-series dataset of SSM/I-derived SWE for 1 March of each year from 1988 to 1998 has been produced as a MAGS deliverable, which provides important information on the spatial and temporal variability in snow cover over the Mackenzie River basin. This dataset has been used in the assessment of snow-cover outputs from MAGS hydrological and climate-modelling investigations. (Au)

F, H
Accumulation; Hydrology; Plant cover; Plant distribution; Satellites; Snow cover; Snow surveys; Snow water equivalent; Special Sensor Microwave/Imager; Temporal variations; Watersheds

G0812, G0811, G0821, G0822, G0823
Athabasca, Lake, region, Alberta/Saskatchewan; Great Bear Lake region, N.W.T.; Great Slave Lake region, N.W.T.; Liard River, British Columbia/N.W.T./Yukon; Mackenzie River region, N.W.T.; Peace River region, Alberta/British Columbia; Peel River region, N.W.T./Yukon


Streamflow in the Mackenzie basin, Canada   /   Woo, M.-K.   Thorne, R.
(Arctic, v. 56, no. 4, Dec. 2003, p. 328-340, ill., maps)
Appendix.
References.
ASTIS record 52865.
Languages: English
Web: http://pubs.aina.ucalgary.ca/arctic/Arctic56-4-328.pdf
Web: doi:10.14430/arctic630
Libraries: ACU

Rivers of the Mackenzie Basin exhibit several seasonal flow patterns that include the nival (snowmelt dominated), proglacial (influenced by glacier melt), wetland, prolacustrine (below large lakes), and regulated flow regimes. The Mackenzie amalgamates and moderates these regimes to deliver spring peak flows, followed by declining summer discharge and low winter flows, to the Arctic Ocean. The mountainous sub-basins in the west (Liard, Peace, and northern mountains) contribute about 60% of the Mackenzie flow, while the interior plains and eastern Canadian Shield contribute only about 25%, even though the two regions have similar total areas (each occupying about 40% of the total Mackenzie Basin). The mountain zone is the dominant flow contributor to the Mackenzie in both high-flow and low-flow years. A case study of the Great Slave system demonstrates the effects of natural runoff, regulated runoff, and lake storage on streamflow, as well as the large year-to-year variability of lake levels and discharge. Despite a warming trend in the past three decades, annual runoff of the Mackenzie Basin has not changed. Significant warming at most climatic stations in April (and at some, also in May or June) could have triggered earlier snowmelt. The first day of hydrograph rise for the main trunk of the Mackenzie (seen as a proxy for breakup) has advanced by about three days per decade, though the trend was not statistically significant for the mountain rivers. Peak flows do not reveal any trend, but the arrival of the spring peaks has become more variable. More evidence is needed to interpret these flow phenomena properly. (Au)

F, G, E, N
Atmospheric temperature; Breakup; Climate change; Evaporation; Floods; Glacial melt waters; Groundwater; Hydrography; Hydrology; Lake ice; Lakes; Measurement; Precipitation (Meteorology); Reservoirs; River discharges; River ice; Rivers; Runoff; Seasonal variations; Snowmelt; Stream flow; Temporal variations; Water level; Watersheds; Weather stations; Wetlands

G0812, G0811, G0821, G0822, G0823
Alberta, Northern; Arctic Red River, N.W.T.; Athabasca River, Alberta; Athabasca, Lake, Alberta/Saskatchewan; British Columbia, Northern; Great Bear Lake region, N.W.T.; Great Bear River, N.W.T.; Great Slave Lake region, N.W.T.; Lesser Slave River, Alberta; Liard River, British Columbia/N.W.T./Yukon; Mackenzie River region, N.W.T.; Mackenzie River, N.W.T.; N.W.T.; Ogilvie River, Yukon; Peace River, Alberta/British Columbia; Peel River, N.W.T./Yukon; Saskatchewan, Northern; Slave River, Alberta/N.W.T.; Williston Lake, British Columbia; Yukon


Science meets traditional knowledge : water and climate in the Sahtu (Great Bear Lake) region, Northwest Territories, Canada   /   Woo, M.-K.   Modeste, P.   Martz, L.   Blondin, J.   Kochtubajda, B.   Tutcho, D.   Gyakum, J.   Takazo, A.   Spence, C.   Tutcho, J.   Di Cenzo, P.   Kenny, G.   Stone, J.   Neyelle, I.   Baptiste, G.   Modeste, M.   Kenny, B.   Modeste, W.
(Arctic, v. 60, no. 1, Mar. 2007, p. 37-46, ill., maps)
References.
ASTIS record 61119.
Languages: English
Web: http://pubs.aina.ucalgary.ca/arctic/Arctic60-1-37.pdf
Web: doi:10.14430/arctic263
Libraries: ACU

In July 2005, several scientists from the Mackenzie GEWEX (Global Energy and Water Cycle Experiment) Study, known as MAGS, met with aboriginal people in Deline on the shore of Great Bear Lake to exchange information on climate and water in the region. Topics discussed pertained directly to the northern environment, and they included climate variability and change, wind, lightning, lake ice, lake level, and streamflow. The traditional knowledge shared by the residents is a rich source of local expertise about the landscape and climate systems of the Deline area, while the scientific knowledge provided by MAGS presents a scientific basis for many observed climate and water phenomena, particularly on a broad regional scale. Through cordial and open discussions, the meeting facilitated the sharing of traditional knowledge and scientific results. The meeting enhanced the potential for traditional knowledge to help direct and validate scientific investigations and for scientific knowledge to be used in conjunction with traditional knowledge to guide community decision making. (Au)

E, F, G, H, N, T, X, L
Atmospheric temperature; Breakup; Climate change; Communication; Elders; Forest fires; Formation; Lake ice; Lightning; Meteorology; Metis; North Slavey Indians; Precipitation (Meteorology); Science; Seasonal variations; Spatial distribution; Storm surges; Storms; Stream flow; Temporal variations; Thickness; Traditional knowledge; Velocity; Water level; Water resources; Winds

G0812
Deline, N.W.T.; Fort Simpson, N.W.T.; Great Bear Lake region, N.W.T.; Great Bear Lake, N.W.T.; Great Bear River, N.W.T.; Norman Wells, N.W.T.; Porcupine River, N.W.T.; Sahtu Settlement Area, N.W.T.


Cold region atmospheric and hydrologic studies : the Mackenzie GEWEX experience. Volume 1 : atmospheric dynamics. Volume 2 : hydrologic processes   /   Woo, M.-k. [Editor]
New York : Springer, 2008.
2 v. (xxiii, 470; xxi, 507 p.) : ill., maps ; 24 cm.
ISBN 978-3-540-73935-7, 978-3-540-74927-1
References.
ASTIS record 65385.
Languages: English
Libraries: ACU

... [Volume 1] presents decade-long advances in atmospheric research in the Mackenzie River Basin in northern Canada, which encompasses environments representative of most cold areas on Earth. Collaborative efforts by a team of about 100 scientists and engineers have yielded knowledge readily transferable to other high latitude regions in America, Europe and Asia. Emphases are placed on the investigation of processes (including storm genesis, precipitation, moisture and energy fluxes), and on the improvement and application of a suite of models and remote sensing to enhance the assessment of climate variability and water resources. This book complements the second volume "Cold Region Atmospheric and Hydrologic Studies. The Mackenzie GEWEX Experience. Volume 2: Hydrologic Processes." Together these books provide a unique synthesis of atmospheric and hydrologic findings and an integrative approach across disciplines in addressing major research issues of cold regions. (Au)

E, F, H, A, C, G, A
Active layer; Aerosols; Albedo; Atmospheric circulation; Atmospheric temperature; Breakup; Climate change; Clouds; Effects monitoring; Effects of climate on ice; Evaporation; Flood forecasting; Floods; Forest fires; Frozen ground; Hydrology; Ice jams; Infrared remote sensing; Lake ice; Lakes; Land classification; Mapping; Mathematical models; Measurement; Moisture transfer; Passive microwave remote sensing; Plant cover; Plant-water relationships; Precipitation (Meteorology); Radiation budgets; Remote sensing; River discharges; River ice; Runoff; Satellite photography; Satellites; Seasonal variations; Snow; Snow cover; Snow water equivalent; Snowmelt; Soil moisture; Solar radiation; Storms; Stream flow; Sublimation; Surface properties; Temporal variations; Thawing; Water vapour; Watersheds; Weather forecasting; Wetlands; Winds

G0812, G0822, G0823, G0811, G0821
Athabasca, Lake, Alberta/Saskatchewan; Great Bear Lake, N.W.T.; Great Slave Lake, N.W.T.; Inuvialuit Settlement Region, N.W.T./Yukon; Liard River, British Columbia/N.W.T./Yukon; Mackenzie Delta, N.W.T.; Mackenzie Delta, Yukon; Mackenzie River region, N.W.T.; Peace River, Alberta/British Columbia; Prairie Provinces; United States


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