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The ASTIS database cites the following 34 publication(s) by John Yackel. Publications are listed from newest to oldest. Please tell us about publications that are not yet cited in ASTIS.


Multifrequency microwave backscatter from a highly saline snow cover on smooth first-year sea ice : first-order theoretical modeling   /   Nandan, V.   Geldsetzer, T.   Yackel, J.J.   Islam, T.   Gill, J.P.S.   Mahmud, M.
(IEEE transactions on geoscience and remote sensing, v. ?, no. ?, 2016, 14 p., ill., maps)
References.
ASTIS record 82978.
Languages: English
Web: doi:10.1109/TGRS.2016.2638323
Libraries: ACU

A theoretical understanding of a multifrequency microwave approach to understand complex microwave interactions from a highly saline snow cover on a relatively smooth first-year sea ice is presented. We examine the sensitivity of Ku-, X-, and C-band sigma0VV and sigma0HH to variability in snow geophysical properties such as salinity, density, temperature, and snow grain radius, sampled from a highly saline snow cover on first-year sea ice. A first-order multilayer snow and ice backscatter model is used to calculate sigma0VV and sigma0HH by taking into account the surface and volume scattering contributions within each snow layer of the snow pack. Penetration depth models are used to calculate the potential penetration of all three frequencies, at initial and perturbed snow property conditions. Sensitivity analyses suggest that variability in salinity and snow grain radius have the greatest effect, followed by density and temperature. This phenomenon is observed for all three frequencies, influencing microwave penetration and backscatter. Dielectric loss associated with highly saline snow covers and substantial changes in scattering contributions from snow grain radius perturbations were found to be the dominant factors affecting microwave penetration and backscatter. Results from this paper demonstrate the potential of using a multifrequency theoretical approach to correlate with active microwave observations to determine the geophysical and electrical state of snow/sea ice system. The paper also represents an evolution in a theoretical understanding on how an active microwave approach using multiple frequencies can be further utilized toward the development of snow thickness and/or snow water equivalent algorithm on smooth FYI. (Au)

G, E, F
Density; Electrical properties; Mathematical models; Radar; Salinity; Sea ice; Snow cover; Surface properties; Temperature; Thickness

G0813
Resolute Bay, Nunavut


All-season compact-polarimetry C-band SAR observations of sea ice   /   Geldsetzer, T.   Arkett, M.   Zagon, T.   Charbonneau, F.   Yackel, J.J.   Scharien, R.K.
(Canadian journal of remote sensing, v. 41, no. 5, 2015, p. 485-504, ill.)
References.
ASTIS record 82464.
Languages: English
Web: doi:10.1080/07038992.2015.1120661
Libraries: ACU

Compact-polarimetry (CP) synthetic aperture radar (SAR) observations are presented for major sea ice types in each ice season. CP data for three wide-swath Radarsat Constellation Mission (RCM) modes were simulated and evaluated. Regression models and statistical distances as functions of incidence angles were calculated for 26 CP parameters, based on 969 samples of user-selected homogeneous regions of sea ice. CP parameters, best able to discriminate sea ice types and open water, were quantitatively identified in three incidence angle ranges (19–29°, 30–39°, 40–49°). These parameters will likely provide discrimination of sea ice types and open water for both visual interpretation and automated classification. Several parameter–ice type combinations exhibit novel scattering responses, which present new opportunities for ice type discrimination and for inferring scattering mechanisms. Specifically, phase-related parameters with early-stage ice types provide discrimination for ice type pairings that are difficult with co- or dual-polarized data. CP parameters change with incidence angle, which necessitates the use of certain CP parameters at smaller incidence angles and others at larger incidence angles in wide-swath RCM modes. The Canadian Ice Service will implement CP SAR data in their operational workflows once the RCM is operational. Prelaunch study results provide a valuable resource for early adoption of CP data. (Au)

G, A, D
Mathematical models; SAR; Satellite photography; Sea ice; Sea water; Seasonal variations; Surface properties

G0813, G0812
Amundsen Gulf, N.W.T.; Barrow Strait, Nunavut; McDougall Sound, Nunavut


Sensitivity of C-band synthetic aperture radar polarimetric parameters to snow thickness over landfast smooth first-year sea ice   /   Gill, J.P.S.   Yackel, J.J.   Geldsetzer, T.   Fuller, M.C.
(Remote sensing of environment, v.166, 1 Sept. 2015, p. 34-49, ill., maps)
References.
ASTIS record 80830 describes the thesis to which this chapter, published as a separate manuscript, belongs.
ASTIS record 80988.
Languages: English
Web: doi:10.1016/j.rse.2015.06.005
Libraries: ACU

C-band linear and polarimetric parameters derived from synthesis and decomposition of Radarsat-2 SAR data are analyzed and evaluated with respect to snow covers of variable thickness on smooth first year sea ice (SFYI). The study is conducted for two selected temperature conditions: 1) cold (7.9 °C) and 2) warm (0.4 °C). First, the polarimetric SAR response from the snow cover at cold conditions is analyzed with an objective to investigate the sensitivity of linear and polarimetric backscatter to snow thickness. Second, the changes in these sensitivities are examined as a function of change in surface air temperature (from 7.9 °C to 0.4 °C) through the changes manifested in snow geophysical properties. The dependence of linear and polarimetric backscatter response on radar incidence angle for different snow thicknesses is also evaluated. Our results demonstrate strong to weak relationships between the polarimetric parameters and snow thickness under cold conditions but virtually no relationship under warm conditions. The strength of this sensitivity varies with parameter type, radar incidence angle and snow geophysical properties. Under the cold conditions, fourteen polarimetric parameters demonstrate a positive relationship and nine demonstrate a negative relationship with snow thickness. This parameter sensitivity to snow thickness indicates an increase in volume or mixed scattering component with increase in snow thickness. The cause of this is primarily an increased microwave interaction with a greater number of dry snow grains, and/or more interaction with increased brine volumes in the brine-wetted snow and upper sea ice layer. A comparison of polarimetric signatures at warm conditions to that at cold conditions shows both an increase and a decrease in response for all snow thicknesses. For thin or medium snow cover, every time a polarimetric parameter response increases or decreases as a consequence of an increase in temperature there is always an opposite response in the same polarimetric parameter for thick snow cover. This is primarily due to the masking effect of moist-snow, likely caused by reduced penetration depth resulting in dominant surface scattering from the air/moist snow interface, and/or the dry snow-brine-wetted snow interface, as opposed to the snow-ice interface. Normal probability density functions (PDFs) employed to determine the snow thickness separation capability of polarimetric parameters show near overlapping signatures of all snow classes under warm conditions, suggesting that snow thickness estimation using snow thermodynamics at warm conditions is not possible. (Au)

G, A, E
Albedo; Atmospheric temperature; Fast ice; Mathematical models; Melting; Ocean-atmosphere interaction; Physical properties; Radar; Salinity; SAR; Sea ice; Snow; Snow cover; Surface properties; Thermal properties; Thermodynamics; Water content of snow

G0815, G0812
Franklin Bay, N.W.T.; Parry Peninsula, N.W.T.


C-band backscatter from a complexly-layered snow cover on first-year sea ice   /   Fuller, M.C.   Geldsetzer, T.   Gill, J.P.S.   Yackel, J.J.   Derksen, C.
(Eastern Snow Conference special issue 2014 / Edited by M. Pelto and R. Kelly. Hydrological processes, v. 28, no. 16, 30 July 2014, p.4614-4625, ill., maps)
References.
Article first published online: 25 June 2014.
ASTIS record 79877.
Languages: English
Web: doi:10.1002/hyp.10255
Libraries: ACU

We present a case study of observed and modelled C-band microwave backscatter signatures for a complexly-layered snow cover on smooth, land-fast, first-year sea ice. We investigate how complexly-layered snow affects the backscatter, by comparing signatures with those for a simple snow cover, and through model sensitivity analysis. Backscatter signatures are obtained using a surface-based scatterometer, on sea ice in Hudson Bay, Canada. Coincident in situ snow and ice geophysical measurements, and on-ice meteorological observations, describe the snow cover formation and structure. A multilayer snow and ice backscatter model is used to iteratively add and subtract components of the complex snow cover to assess their impacts on the overall backscatter. For incidence angles between 20° and 70°, the backscatter from a complex snow cover on smooth first-year sea ice is significantly higher than backscatter from a simple snow cover on similar sea ice. Sensitivity analysis suggests that rough ice layers formed within the complex snow cover and those superimposed at the sea ice interface are the physical mechanisms that affect an increase in surface and volume backscattering. This has implications for sea ice mapping, geophysical inversion and snow thickness studies. (Au)

F, E, A, G
Ablation; Climate change; Density; Fast ice; Formation; Mathematical models; Meteorology; Microwave radiation; Rain; SAR; Sea ice; Seasonal variations; Snow; Snow cover; Surface properties; Temporal variations; Thickness

G0814
Hudson Bay


Analysis of consistency in first-year sea ice classification potential of C-band SAR polarimetric parameters   /   Gill, J.P.S.   Yackel, J.J.   Geldsetzer, T.
(Canadian journal of remote sensing, v. 39, no. 2, Apr. 2013, p. 101-117, ill., map)
References.
ASTIS record 78014.
Languages: English
Web: doi:10.5589/m13-016
Libraries: ACU

The consistency in first-year sea ice classification potential of C-band SAR polarimetric parameters was analyzed by comparing the results of two studies conducted for the same ice types under different geophysical settings. The SAR images used in the comparison were acquired at an incidence angle difference of 4°. Probability density functions, grey level parameter images, and classification statistics derived using k-means classifier were used in the comparative analysis. The investigation showed that not all polarimetric parameters exhibit consistency in their classification performance under different geophysical settings. Out of the 20 polarimetric parameters analyzed, 12 demonstrated high levels of classification consistency between the two studies. Among these 12 parameters, only four possessed high classification accuracy and could be applicable for sea ice classification under variable environmental conditions. The parameters that showed the highest classification accuracies in both the studies were found to be inconsistent in their ice type separation capabilities. The signatures of these parameters differed for one or more ice types when compared between the two studies. The utility of these parameters in individual sea ice classification studies is recommended but their relevance in generalized sea ice classification scheme is unclear. (Au)

G, A, E, F
Classification; Density; Fast ice; Identification; Mathematical models; Melting; Meteorology; Quality assurance; Radar; SAR; Sea ice; Snow; Surface properties; Thermodynamics

G0815, G0812
Franklin Bay, N.W.T.; Parry Peninsula, N.W.T.


Polarimetric Synthetic Aperture Radar measurements of snow covered first-year sea ice   /   Hossain, M.   Yackel, J.J. [Supervisor]
Calgary, Alta. : University of Calgary, 2012.
xx, 95 p. : ill., maps ; 28 cm.
(ProQuest Dissertations & Theses publication, no. NR92636)
ISBN 978-0-494-92636-9
Thesis (M.Sc.) - University of Calgary, Calgary, Alta., 2012.
Indexed from a PDF file acquired from ProQuest Dissertations & Theses.
Appendices.
Bibliography: p. 79-91.
ASTIS record 79698.
Languages: English
Web: http://www.collectionscanada.gc.ca/obj/thesescanada/vol2/002/MR92636.pdf
Libraries: ACU

This study examines the utility of fully polarimetric C-and SAR parameters and three-component scattering model to quantify the sensitivity of snow covered first-year sea ice (FYI) to radar incidence angles and surface air temperature (SAT) during the late winter transition. This three component scattering model is based on surface, double-bounce and volume scattering contributed from various materials and surface properties. RADARSAT-2 C-band fully polarimetric synthetic aperture radar (POLSAR) data is utilized to quantify the sensitivity of thermodynamic effects (-8° and -4°C) of the polarimetric backscatter signature on mean snow cover thickness ranging from 8 cm to 36 cm with in-situ geophysical data from four different validation sites along with two different radar incidence angles 29° (steep) and 39° (shallow) to discriminate between snow-covered smooth, rough and deformed FYI. The result shows enhanced discrimination at shallower incidence angles compared to steeper ones in both 2-D and 3-D plots. The double-bounce scattering contribution is low for all FYI types at both incidence angles which are attributed to shallower incidence angle as microwave energy being in direct contact with a greater volume of higher dielectric brine coated, enlarged snow grains in the basal layer compared to the steeper incidence angles. The results also show that surface scattering dominates for all three FYI types at both incidence angles and decreases with increasing surface roughness and radar incidence angles whereas opposite results observed for volume scattering mechanisms. The results indicate that higher variation measured for thin snow class ~7 dB for both co- cross-polarization backscatters compared to thick class ~1 dB which corroborates with electro-thermodynamic theory. (Au)

G, D, E, F
Atmospheric temperature; Climate change; Density; Diurnal variations; Electrical properties; Fast ice; Formation; Ice cover; Ice fog; Mathematical models; Melting; Ocean temperature; Ocean-atmosphere interaction; Pack ice; Physical properties; Salinity; SAR; Satellites; Sea ice; Seasonal variations; Snow; Snow cover; Spatial distribution; Surface properties; Temporal variations; Thermal properties; Thermal regimes; Thermodynamics; Theses; Thickness; Water masses

G0814, G07
Churchill, Cape, waters, Manitoba; Franklin Bay, N.W.T.; Hudson Bay


Geophysical controls on C band polarimetric backscatter from melt pond covered Arctic first-year sea ice : assessment using high-resolution scatterometry   /   Scharien, R.K.   Yackel, J.J.   Barber, D.G.   Asplin, M.   Gupta, M.   Isleifson, D.
(Journal of geophysical research, v.117, C00G18, Sept. 2012, 15 p., ill., map)
References.
ASTIS record 77010.
Languages: English
Web: doi:10.1029/2011JC007353
Libraries: ACU

Geophysical controls on C band polarimetric backscatter from the discrete surface cover types which comprise advanced melt first-year sea ice (FYI): snow covered ice, bare ice, and melt pond; are assessed using polarimetric radar scatterometry from test sites representing high Arctic and marginal ice zones in the Canadian Arctic. Surface characterization data is used to evaluate the interaction of polarized radiation with each feature, and dominant scattering mechanisms are assessed in a regional context. High-resolution time series (diurnal) scatterometry and coincident atmospheric boundary layer profile data are used to explain linkages between ice-atmosphere interactions and polarimetric backscatter in a marginal ice zone. The co-polarization ratio for FYI melt ponds is shown to be distinct from snow covered ice or bare ice during early and peak phases of advanced melt, making it a candidate parameter for the unambiguous detection of pond formation and the inversion of melt pond fraction. The ratio displays an increasing trend with radar incidence angle in a manner consistent with Bragg surface scattering theory, though it is not predictable by a Bragg model. Cross-polarization backscatter intensity shows potential for discriminating the onset and duration of freeze events in a marginal ice zone, due to dominant backscatter from the snow cover adjacent to melt ponds. Preliminary results here outline the potential of covariance matrix derived polarimetric measurements for the inversion of advanced melt sea ice geophysical parameters, and provide a basis for the investigation of distributed targets in late season spaceborne polarimetric SAR scenes. (Au)

G, E, A, F
Ablation; Albedo; Atmospheric humidity; Atmospheric temperature; Boundary layers; Clouds; Cores; Crystals; Density; Detection; Diurnal variations; Electrical properties; Fast ice; Formation; Infrared remote sensing; Instruments; Mapping; Mathematical models; Melting; Meteorology; Microwave radiation; Ocean-atmosphere interaction; Optical properties; Passive microwave remote sensing; Physical properties; Puddles; Salinity; SAR; Satellite photography; Sea ice; Seasonal variations; Size; Slush; Snow; Solar radiation; Spatial distribution; Surface properties; Temperature; Temporal variations; Thickness; Velocity; Winds

G0815
Allen Bay, Nunavut; Darnley Bay, N.W.T.


Evaluation of C-band SAR polarimetric parameters for discrimination of first-year sea ice types   /   Gill, J.P.S.   Yackel, J.J.
(Special issue : RADARSAT-2, part 2. Canadian journal of remote sensing, v. 38, no. 3, June 2012, p. 306-323, ill., maps)
References.
ASTIS record 76592.
Languages: English
Web: doi:10.5589/m12-025
Libraries: ACU

In this study, the classification potential of polarimetric parameters derived after Cloude-Pottier decomposition, Touzi decomposition, Freeman Durden decomposition, normalized radar cross section measurements, phase differences, and statistical synthetic aperture radar correlation measures is evaluated by relating them to three pre-identified sea ice types and wind-roughened open water. A combined approach that constitutes a visual inspection of estimated probability densities of the polarimetric parameters and quantitative analysis using supervised classifications (k means and maximum likelihood) is adopted. Polarimetric parameters are iteratively combined in pairs and triplets to test for their ice type discrimination potential. Sensitivity of polarimetric parameters to radar incidence angle is also examined. Our results demonstrated strong but variable sensitivity of polarimetric parameters to different ice types, which was dependent on radar incidence angle. Results of parameter evaluation demonstrated that no single parameter discriminates significantly (>60%) between all the ice types considered in the study. Combining two low correlated parameters increased the classification accuracy by 10%-22%. Combining the third polarimetric parameter did not necessarily improve the classification results. However, the best classification results were achieved using a combination of three parameters. (Au)

G, A, E
Classification; Fast ice; Identification; Mathematical models; Melting; Meteorology; Quality assurance; Radar; SAR; Sea ice; Surface properties; Thermodynamics

G0815
Franklin Bay, N.W.T.


Correction to "Trends and variability in summer sea ice cover in the Canadian Arctic based on the Canadian Ice Service Digital Archive, 1960-2008 and 1968-2008"   /   Tivy, A.   Howell, S.E.L.   Alt, B.   McCourt, S.   Chagnon, R.   Crocker, G.   Carrieres, T.   Yackel, J.J.
(Journal of geophysical research, v.116, no. C6, June 2011, 2 p.)
ASTIS record 73162 describes the original article which this "correction" ammends.
ASTIS record 79116.
Languages: English
Web: doi:10.1029/2011JC007248
Libraries: ACU

[1] In the paper "Trends and variability in summer sea ice cover in the Canadian Arctic based on the Canadian Ice Service Digital Archive, 1960-2008 and 1968-2008" by A. Tivy et al. (Journal of Geophysical Research, 116, C03007, doi:10.1029/2009JC005855, 2011) several data from Table 1 were missing. The corrected Table 1 appears here. (Au)

G, E, A
Aerial surveys; Atmospheric circulation; Atmospheric pressure; Atmospheric temperature; Climate change; Climatology; Databases; Effects of climate on ice; Ice cover; Ice floes; Infrared remote sensing; Mapping; Maps; Melting; Passive microwave remote sensing; Quality assurance; Radar; SAR; Satellite photography; Sea ice; Seasonal variations; Size; SLAR; Spatial distribution; Special Sensor Microwave/Imager; Temporal variations

G0815, G07, G09, G0814
Alaskan Beaufort Sea; Baffin Bay-Davis Strait; Canadian Arctic Islands waters; Canadian Beaufort Sea; Hudson Bay; Northwest Passage


Origins and levels of seasonal forecast skill for sea ice in Hudson Bay using canonical correlation analysis   /   Tivy, A.   Howell, S.E.L.   Alt, B.   Yackel, J.J.   Carrieres, T.
(Journal of climate, v. 24, no. 5, Mar. 2011, p.1378-1395, ill., maps)
References.
ASTIS record 73163.
Languages: English
Web: doi:10.1175/2010JCLI3527.1
Libraries: ACU

Canonical correlation analysis (CCA) is used to estimate the levels and sources of seasonal forecast skill for July ice concentration in Hudson Bay over the 1971 to 2005 period. July is an important transition month in the seasonal cycle of sea ice in Hudson Bay because it is the month when the sea ice clears enough to allow the first passage of ships to the Port of Churchill. Sea surface temperature (quasi-global, North Atlantic and North Pacific), Northern Hemisphere 500mb geopotential height (z500) and sea level pressure (SLP), and regional surface air temperature (SAT) are tested as predictors at 3, 6 and 9 month lead times. The model with the highest skill has three predictors, fall North Atlantic SST, fall z500, fall SAT, and significant tercile forecast skill covering 61% of the Hudson Bay region. The highest skill for a single predictor model is from fall North Atlantic SST (6-month lead). Fall SST explains 69% of the variance in July ice concentration in Hudson Bay and a possible atmospheric link that accounts for the lagged relationship is presented. CCA diagnostics suggest that changes in the sub-polar North Atlantic gyre and the Atlantic Multidecadal Oscillation (AMO), reflected in sea surface temperature, precedes a deepening/weakening of the winter upper air ridge northwest of Hudson Bay. Changes in the height of the ridge are reflected in the strength of the winter northwesterly winds over Hudson Bay that have a direct impact on the winter ice thickness distribution; anomalies in winter ice severity are later reflected in the pattern and timing of spring break-up. July ice concentration in Hudson Bay has declined by approximate 20% per decade between 1979 and 2007 and the hypothesized link to the AMO may help explain this significant loss of ice. (Au)

G, D, E
Atmospheric pressure; Atmospheric temperature; Breakup; Climatology; Databases; Effects of climate on ice; Forecasting; Ice cover; Melting; Ocean temperature; Sea ice; Seasonal variations; Spatial distribution; Temporal variations; Thickness; Winds

G0814, G0815, G11
Hudson Bay; Hudson Strait, Nunavut/Québec; North Atlantic Ocean


Trends and variability in summer sea ice cover in the Canadian Arctic based on the Canadian Ice Service Digital Archive, 1960-2008 and 1968-2008   /   Tivy, A.   Howell, S.E.L.   Alt, B.   McCourt, S.   Chagnon, R.   Crocker, G.   Carrieres, T.   Yackel, J.J.
(Journal of geophysical research, v.116, no. C3, Mar. 2011, 25 p., ill., maps)
Appendix.
References.
ASTIS record 73162.
Languages: English
Web: doi:10.1029/2009JC005855
Libraries: ACU

The Canadian Ice Service Digital Archive (CISDA) is a compilation of weekly ice charts covering Canadian waters from the early 1960s to present. The main sources of uncertainty in the database are reviewed and the data are validated for use in climate studies before trends and variability in summer averaged sea ice cover are investigated. These data revealed that between 1968 and 2008, summer sea ice cover has decreased by 11.3% ±2.6%/decade in Hudson Bay, 2.9% ±1.2%/decade in the Canadian Arctic Archipelago (CAA), 8.9% ±3.1%/decade in Baffin Bay, and 5.2% ±2.4%/decade in the Beaufort Sea with no significant reductions in multiyear ice. Reductions in sea ice cover are linked to increases in early summer surface air temperature (SAT); significant increases in SAT were observed in every season and they are consistently greater than the pan-Arctic change by up to ~0.2°C/decade. Within the CAA and Baffin Bay, the El Niño-Southern Oscillation index correlates well with multiyear ice coverage (positive) and first-year ice coverage (negative) suggesting that El Niño episodes precede summers with more multiyear ice and less first-year ice. Extending the trend calculations back to 1960 along the major shipping routes revealed significant decreases in summer sea ice coverage ranging between 11% and 15%/decade along the route through Hudson Bay and 6% and 10%/decade along the southern route of the Northwest Passage, the latter is linked to increases in SAT. Between 1960 and 2008, no significant trends were found along the northern western Parry Channel route of the Northwest Passage. (Au)

G, E, A
Aerial surveys; Atmospheric circulation; Atmospheric pressure; Atmospheric temperature; Climate change; Climatology; Databases; Effects of climate on ice; Ice cover; Ice floes; Infrared remote sensing; Mapping; Maps; Melting; Passive microwave remote sensing; Quality assurance; Radar; SAR; Satellite photography; Sea ice; Seasonal variations; Size; SLAR; Spatial distribution; Special Sensor Microwave/Imager; Temporal variations

G0815, G07, G09, G0814
Alaskan Beaufort Sea; Baffin Bay-Davis Strait; Canadian Arctic Islands waters; Canadian Beaufort Sea; Hudson Bay; Northwest Passage


Physical, dielectric, and C band microwave scattering properties of first-year sea ice during advanced melt   /   Scharien, R.K.   Geldsetzer, T.   Barber, D.G.   Yackel, J.J.   Langlois, A.
(Journal of geophysical research, v.115, C12026, 2010, 16 p., ill., maps)
References.
ASTIS record 73179.
Languages: English
Web: doi:10.1029/2010JC006257
Libraries: ACU

This paper investigates the influence of solar heating and intermittent cloud cover on the physical and dielectric properties of naturally snow-free, warm (>-2°), first-year sea ice (FYI) in the southeastern margin of the Beaufort Sea during advanced melt. A simple three-layer physical model describing the surface is introduced and copolarized C band microwave signatures are simulated using a multilayer scattering model forced with four sets of measured surface parameters. Modeled backscatter signatures are compared to coincident surface-based C band scatterometer signatures in order to elucidate the signature controlling properties of the ice. Results show that 50 MHz impedance probe dielectric measurements of desalinated upper ice layers exhibit statistically significant diurnal variations due to the link between solar forcing and the availability of free water in brine-free upper ice layers. Enhanced downwelling longwave radiation to the surface from low-level stratus clouds is positively linearly associated (r = 0.709) with volumetric moisture mv detected in upper ice layers. Model results show that desalinated upper ice layers contribute volume scattering from smooth, snow-free FYI under the observed surface mv range. Sustained cloud-free periods result in the formation of a 0.5-2.5 cm granular surface layer, composed of 5.2 mm ice grains, which enhances backscatter under relatively dry conditions. Sensitivity analyses show that layer thickness plays a significant role in scattering due to the increased number density of inclusions which act as discrete scatterers, and sufficient energy may penetrate to, and scatter from, the saline columnar ice layer under relatively dry conditions only (mv <2%). (Au)

G, E, A
Albedo; Clouds; Cores; Crystals; Diurnal variations; Electrical properties; Gases in ice; Heating; Mathematical models; Melting; Microwave radiation; Passive microwave remote sensing; Physical properties; Puddles; Salinity; Sea ice; Size; Slush; Solar radiation; Spatial distribution; Temperature

G0815
Darnley Bay, N.W.T.; Franklin Bay, N.W.T.


Sea ice type and open water discrimination using dual co-polarized C-band SAR   /   Geldsetzer, T.   Yackel, J.J.
(Canadian journal of remote sensing, v. 35, no. 1, Feb. 2009, p. 73-84, ill., maps)
References.
ASTIS record 74091.
Languages: English
Web: doi:10.5589/m08-075
Libraries: ACU

We investigate the utility of dual co-polarized C-band synthetic aperture radar (SAR) imagery for discriminating sea ice types and open water during winter. We base our analysis on ENVISAT ASAR alternating vertical and horizontal polarization (VV, HH) medium-resolution imagery of thin sea ice, first-year sea ice, multiyear sea ice, and open water in the Canadian Arctic. We introduce a methodology for generating colour composite imagery (based on VV, HH, and co-polarization ratio channels) that substantially enhances visual discrimination. We statistically compare sampled vertical and horizontal backscatter from sea ice types and open water to assess backscatter magnitudes and polarization differences. The latter are presented as co-polarized ratio (VV/HH) values in decibels (dB). We conclude by presenting a decision-tree classifier using estimated statistical thresholds. Open water is unambiguously discriminated (>99% accuracy) from all sea ice types, except thin sea ice, using a co-polarized ratio threshold of 2 dB. Thin sea ice exhibits high variability in backscatter magnitude and polarization difference, making its discrimination from multiyear sea ice, rough first-year sea ice, and open water ambiguous. Thin sea ice is effectively discriminated (93% accuracy) from smooth first-year sea ice using a co-polarized ratio threshold of 1.3 dB. Smooth snow-covered first-year sea ice exhibits polarization differences that are attributed to volume scattering mechanisms within the brine-wetted snow cover. (Au)

G, A, F, E
Atmospheric temperature; Classification; Electrical properties; Identification; Physical properties; SAR; Satellite photography; Sea ice; Sea water; Snow; Spatial distribution; Surface properties; Thickness; Velocity; Water content of snow; Winds

G0815
Barrow Strait, Nunavut; Cornwallis Island waters, Nunavut; McDougall Sound, Nunavut; Peel Sound, Nunavut; Queens Channel, Nunavut; Wellington Channel, Nunavut


Investigations of snow thickness on first-year sea ice from in-situ and polarimetric SAR data   /   Fuller, M.C.   Yackel, J.J.   Iacozza, J.
In: Circumpolar Flaw Lead System Study, International Polar Year, 2007-2008 : meeting materials, CFL All-Hands Meeting, 1-5 November 2009, Winnipeg / University of Manitoba. - [Winnipeg, Man.] : University of Manitoba, 2009, p. 26
Abstract of an oral presentation.
ASTIS record 69713.
Languages: English
Libraries: ACU

This study will present polarimetric C-band backscatter observations of snow on first-year sea ice during the spring melt period in Franklin Bay, Beaufort Sea. The recent decrease in Arctic sea ice extent has the potential to open the region to transportation, resource, and economic development; changes that will impact human, wildlife, and environmental concerns. Snow cover plays an important role in both the formation and ablation of sea ice through insulating and albedo effects. It is important to parameterize, quantify, and forecast snowcover properties for modeling Arctic sea ice trends with respect to climate change. The role of snow on sea ice is understood; however, current parameterization of snowcover relies primarily upon passive microwave data which is attenuated as water forms in snow; therefore, snowcover is rarely accurately represented during seasonal melt regimes. The data set consists of RADARSAT-2 backscatter and in situ snow depth data collected in April and May of 2008 in Franklin Bay. Transect data over rough, intermediate, and smooth first-year land-fast sea ice from the study period will be presented. The goal of this work is to derive relationships between polarimetric response and change in snow depth with melt onset for various ice types. Modeled relationships will be inverted in order to estimate snow depth from RADARSAT-2 polarimetric SAR data. (Au)

F, G, A
Albedo; Fast ice; Melting; Passive microwave remote sensing; SAR; Snow ; Surface properties; Thickness; Water content of snow

G0815
Franklin Bay, N.W.T.


Application of satellite remote sensing techniques for estimating air-sea CO2 fluxes in Hudson Bay, Canada during the ice-free season   /   Else, B.G.T.   Yackel, J.J.   Papakyriakou, T.N.
(Remote sensing of environment, v.112, no. 9, 15 Sept. 2008, p.3550-3562, ill., maps)
References.
ASTIS record 74256.
Languages: English
Web: doi:10.1016/j.rse.2008.04.013
Libraries: ACU

The role of coastal seas as either a sink or a source of CO2 is subject to a great deal of uncertainty. This uncertainty largely arises from a lack of observations in the coastal zones. Remote sensing offers an avenue for expanding these observations by allowing for the extrapolation of relatively limited data sets of dissolved CO2 (p(CO2)sw). In this paper, predictive algorithms for p(CO2)sw that could be applied to remote sensing products were created from a field data set collected from September-October, 2005 in Hudson Bay, Canada. The field data showed that an effective p(CO2)sw interpolation algorithm could be created using sea surface temperature (SST) as a predictor, and that a slight improvement of the algorithm could be achieved if measurements of absorption due to coloured dissolved organic material (aCDOM) were included. Unfortunately, satellite retrievals of aCDOM did not match well with in situ observations, and so only SST (obtained from the MODIS Aqua sensor) was used to create monthly maps of p(CO2)sw for the period of August-October. To estimate fluxes of CO2, constructed surfaces of p(CO2)sw were combined with estimates of gas transfer velocity derived from QuikSCAT wind retrievals, and p(CO2)air based on field observations. The results of these calculations revealed that Hudson Bay acts as a source of CO2 during August and September, but reverts to a sink of CO2 in October as the water temperature decreases. Overall, a positive flux of 1.60 Tg C was estimated for the region during the ice-free season. This result is in contrast to most Arctic or sub-Arctic continental shelf seas, where usually strong absorptions of CO2 are observed (Au)

D, E, A, F
Atmospheric pressure; Carbon; Carbon cycling; Carbon dioxide; Electrical properties; Electronic data processing; Gases; Ocean currents; Ocean temperature; Ocean-atmosphere interaction; Radar; Remote sensing; River discharges; Salinity; Satellite photography; Satellites; Spatial distribution; Surface temperature; Temporal variations; Velocity; Water masses; Winds

G0814, G0815
Foxe Basin, Nunavut; Hudson Bay; Hudson Strait, Nunavut/Québec


Observations of sea surface fCO2 distributions and estimated air-sea CO2 fluxes in the Hudson Bay region (Canada) during the open water season   /   Else, B.G.T.   Papakyriakou, T.N.   Granskog, M.A.   Yackel, J.J.
(Journal of geophysical research, v.113, no. C8, C08026, Aug. 2008, 12 p., ill., maps)
References.
ASTIS record 74148.
Languages: English
Web: doi:10.1029/2007JC004389
Libraries: ACU

The lack of baseline estimates of air-sea CO2 exchange in Arctic and sub-Arctic regions represents a major shortfall in our ability to understand how climate change may affect CO2 fluxes at high latitudes. The 2005 ArcticNet cruise of Hudson Bay (Canada) provided a rare comprehensive oceanographic survey of one such region. Ship-based observations of sea-surface fugacity of CO2 (fCO2sw) were made at 56 locations between 15 September and 26 October and were found to range from 259 µatm in Hudson Strait to 425 µatm at the entrance to James Bay. Strong relationships between fCO2sw and river discharge were identified, with coastal waters observed to be supersaturated with respect to the atmosphere, while offshore waters were undersaturated. High correlations of fCO2sw with salinity, sea surface temperature, and colored dissolved organic matter suggest that thermodynamic effects and the oxidation of riverine carbon are driving supersaturation in the coastal zone. Calculated instantaneous fluxes of CO2 ranged from +16.5 mmol/m²/d in James Bay to -19.6 mmol/m²/d in Foxe Channel. Using National Centers for Environmental Prediction wind speed climatologies, a net sink in Hudson Bay of -0.73 (±0.4) mmol/m²/d was estimated for study period, substantially lower compared to many other Arctic shelf environments. This initial study provides a preliminary examination of fCO2sw dynamics in Hudson Bay; future analyses and field measurements will be necessary to properly constrain CO2 fluxes in this season and over an annual cycle. (Au)

D, F, E, H
Atmospheric humidity; Atmospheric temperature; Bacteria; Carbon; Carbon dioxide; Chemical oceanography; Chlorophyll; Colored dissolved organic matter; Continental shelves; Electrical properties; Estuaries; Gases; Ocean currents; Ocean temperature; Ocean-atmosphere interaction; Photosynthesis; Primary production (Biology); River discharges; Rivers; Runoff; Salinity; Solar radiation; Spatial distribution; Velocity; Water masses; Winds

G0814, G0815
Foxe Channel, Nunavut; Hudson Bay; Hudson Strait, Nunavut/Québec; James Bay


Multi-year sea-ice conditions in the western Canadian Arctic Archipelago region of the Northwest Passage : 1968-2006   /   Howell, S.E.L.   Tivy, A.   Yackel, J.J.   McCourt, S.
(Atmosphere-ocean, v. 46, no. 2, June 2008, p. 229-242, ill., maps)
References.
ASTIS record 65913.
Languages: English
Web: doi:10.3137/ao.460203
Libraries: ACU

Numerous studies have reported decreases in Arctic sea-ice cover over the past several decades and General Circulation Model (GCM) simulations continue to predict future decreases. These decreases - particularly in thick perennial or multi-year ice (MYI) - have led to considerable speculation about a more accessible Northwest Passage (NWP) as a transit route through the Canadian Arctic Archipelago (CAA). The Canadian Ice Service Digital Archive (CISDA) is used to investigate dynamic import/export and in situ growth of MYI within the western CAA regions of the NWP from 1968 to 2006. This analysis finds that MYI conditions in the western CAA regions of the NWP have remained relatively stable because the M'Clintock Channel and Franklin regions continuously operate as a drain-trap mechanism for MYI. Results also show that in addition to the Queen Elizabeth Islands (QEI) region, the Western Parry Channel and the M'Clintock Channel are also regions where a considerable amount of MYI forms in situ and combined with dynamic imports contributes to heavy MYI conditions. There is also evidence to suggest that more frequent dynamic import of MYI appears to have occurred since-1999 compared to the formation of more MYI in situ before 1999. As a result, the drain-trap mechanism that has historically maintained heavy MYI conditions in the NWP is perhaps operating faster now than it was in the past. Based on the 38-year MYI record examined in this study, it is likely that the mechanisms operating within the western CAA regions of the NWP can facilitate the continued presence of MYI for quite some time. (Au)

G, E, A
Aerial surveys; Albedo; Atmospheric circulation; Atmospheric temperature; Databases; Geographic information systems; Growth; Ice cover; Infrared remote sensing; Melting; Movement; Ocean-atmosphere interaction; Passive microwave remote sensing; Quality assurance; SAR; Satellites; Sea ice; Seasonal variations; SLAR; Spatial distribution; Temporal variations; Winds

G07, G0815
Amundsen Gulf, N.W.T.; Beaufort Sea; Coronation Gulf, Nunavut; Dease Strait, Nunavut; Dolphin and Union Strait, Nunavut; Franklin Strait, Nunavut; M'Clintock Channel, Nunavut; M'Clure Strait, N.W.T.; Peel Sound, Nunavut; Prince of Wales Strait, N.W.T.; Queen Elizabeth Islands waters, N.W.T./Nunavut; Queen Maud Gulf, Nunavut; Victoria Strait, Nunavut; Viscount Melville Sound, N.W.T./Nunavut


On the link between SAR-derived sea ice melt and development of the summer upper ocean mixed layer in the North Open Water Polynya   /   Galley, R.J.   Barber, D.G.   Yackel, J.J.
(International journal of remote sensing, v. 28, no. 18, Sept. 2007, p.3979-3994, ill., maps)
References.
ASTIS record 74143.
Languages: English
Web: doi:10.1080/01431160601105900
Libraries: ACU

We examine the ability of SAR-derived landfast sea ice thermodynamic state surrounding the North Water Polynya to predict the timing of a shallow, stably stratified summer ocean mixed layer in the region. Radarsat-1 ScanSAR is used to derive melt and pond onset dates over landfast sea ice surrounding the polynya, describing its thermodynamic evolution. Salinity and temperature profiles, connected in time and space, are complemented by potential density profiles and mixed layer depths, which describe the evolution of the upper ocean mixed layer between 4 April and 21 July 1998. Surface salinity driven potential density stratification and summer mixed layer depths are temporally coincident. Sea ice-ocean connection is first described at the local scale, then regionally. At the local scale, a reduction in surface salinity occurs between the melt and pond onsets over landfast sea ice. At the polynya scale, interpolated pond onset date is highly effective at predicting the timing of a thin, stably stratified summer ocean mixed layer; this has consequences for the potential prediction of timing of maximum ecosystem productivity. (Au)

G, D, E
Density; Electrical properties; Fast ice; Ice cover; Melting; Ocean temperature; Ocean-atmosphere interaction; Pack ice; Puddles; Salinity; SAR; Sea ice ; Seasonal variations; Spatial distribution; Temporal variations; Thermal properties; Thermal regimes; Water masses

G09
Baffin Bay-Davis Strait; Coburg Island waters, Nunavut; Goding Bay region, Nunavut; North Water Polynya, Baffin Bay; Norton Shaw, Cape, waters, Nunavut; Rensselaer Bugt, Greenland; Rosse Bay, Nunavut; Smith Sound, Greenland/Nunavut


Coincident high resolution optical-SAR image analysis for surface albedo estimation of first-year sea ice during summer melt   /   Scharien, R.K.   Yackel, J.J.   Granskog, M.A.   Else, B.G.T.
(Remote sensing of the cryosphere - special issue / Edited by M. Tedesco. Remote sensing of environment, v.111, no. 2-3, 30 Nov. 2007, p. 160-171, ill., maps)
References.
ASTIS record 74142.
Languages: English
Web: doi:10.1016/j.rse.2006.10.025
Libraries: ACU

The parameterization of sea ice albedo during summer, when fluctuations in the fractional coverage of melt ponds change on a variety of spatial and temporal scales, represents a significant challenge for both the modelling and remote sensing communities. Ubiquitous cloud cover in summer inhibits the use of optical sensors for providing large-scale estimates of sea ice surface albedo. C-band (5.3 GHz) Synthetic Aperture RADAR (SAR) data from ENVISAT-ASAR is compared to coincident surface climatological albedo (alpha) estimates derived from high-resolution Quickbird VIS-NIR imagery in order to demonstrate the utility of high-resolution, dual-polarized (VV, HH) SAR for detecting variations in alpha of melt pond covered landfast first-year sea ice (FYI) adjacent to Hudson Bay. Variations in ice alpha are detected from SAR imagery using the co-polarization ratio (gamma), shown to be significantly correlated (-0.81) with alpha when melt ponds are in liquid form. Results show the use of gamma represents a substantial increase in correlation to alpha when compared to conventional like-polarized SAR backscattering coefficients. A regression model demonstrates that gamma can be used as an estimator for landfast-FYI alpha to within ±5.2% provided: (1) The SAR images at a shallow enough incidence angle to induce separation between like-polarized channels; and (2) the conditions of Bragg surface scattering, characteristic of relatively shallow FYI melt ponds, is met. (Au)

G, A, F, E
Albedo; Atmospheric humidity; Atmospheric temperature; Clouds; Cores; Fast ice; Formation; Infrared remote sensing; Isotopes; Melting; Optical properties; Oxygen; Puddles; Rain; Rivers; Runoff; Salinity; SAR; Satellite photography; Sea ice; Seasonal variations; Snow; Snowmelt; Snowpatches; Spatial distribution; Surface properties; Temporal variations; Thickness; Velocity; Winds

G0814
Button Bay, Nunavut; Churchill, Cape, waters, Manitoba


First-year sea ice spring melt transitions in the Canadian Arctic Archipelago from time-series synthetic aperture radar data, 1992-2002   /   Yackel, J.J.   Barber, D.G.   Papakyriakou, T.N.   Breneman, C.
(Hydrological processes, v. 21, no. 2, 15 Jan. 2007, p. 253-265, ill., maps)
References.
ASTIS record 65915.
Languages: English
Web: doi:10.1002/hyp.6240
Libraries: ACU

This paper synthesizes 10-years' worth of interannual time-series space-borne ERS-1 and RADARSAT-1 synthetic aperture radar (SAR) data collected coincident with daily measurement of snow-covered, land-fast first-year sea ice (FYI) geophysical and surface radiation data collected from the Seasonal Sea Ice Monitoring and Modeling Site, Collaborative-Interdisciplinary Cryospheric Experiment and 1998 North Water Polynya study over the period 1992 to 2002. The objectives are to investigate the seasonal co-relationship of the SAR time-series dataset with selected surface mass (bulk snow thickness) and climate state variables (surface temperature and albedo) measured in situ for the purpose of measuring the interannual variability of sea ice spring melt transitions and validating a time-series SAR methodology for sea ice surface mass and climate state parameter estimation. We begin with a review of the salient processes required for our interpretation of time-series microwave backscatter from land-fast FYI. Our results suggest that time-series SAR data can reliably measure the timing and duration of surface albedo transitions at daily to weekly time-scales and at spatial scales that are on the order of hundreds of metres. Snow thickness on FYI immediately prior to melt onset explains a statistically significant portion of the variability in timing of SAR-detected melt onset to pond onset for SAR time-series that are made up of more than 25 images. Our results also show that the funicular regime of snowmelt, resolved in time-series SAR data at a temporal resolution of approximately 2.5 images per week, is not detectable for snow covers less than 25 cm in thickness. (Au)

G, F, A, E
Albedo; Atmospheric temperature; Cores; Density; Diurnal variations; Energy budgets; Fast ice; Formation; Melting; Puddles; Remote sensing; Salinity; SAR; Satellites; Seasonal variations; Snow; Snow surveys; Snowmelt; Solar radiation; Spatial distribution; Surface temperature; Temperature; Temporal variations; Thermal properties; Thermal regimes; Thermodynamics; Thickness; Weather stations

G09, G0815
Barrow Strait, Nunavut; Cornwallis Island waters, Nunavut; McDougall Sound, Nunavut; North Water Polynya, Baffin Bay; Wellington Channel, Nunavut


Observations of snow water equivalent change on landfast first-year sea ice in winter using synthetic aperture radar data   /   Yackel, J.J.   Barber, D.G.
(IEEE transactions on geoscience and remote sensing, v. 45, no. 4, Apr. 2007, p.1005-1015, ill., maps)
References.
ASTIS record 65914.
Languages: English
Web: doi:10.1109/TGRS.2006.890418
Libraries: ACU

In this paper, we examine the utility of synthetic aperture radar (SAR) backscatter data to detect a change in snow water equivalent (SWE) over landfast first-year sea ice during winter at relatively cold temperatures. We begin by reviewing the theoretical framework for linking microwave scattering from SAR to the thermodynamic and electrical properties of first-year sea ice. Previous research has demonstrated that for a given ice thickness and air-temperature change, a thick snow cover will result in a smaller change in the snow-ice interface temperature than will a thin snow cover. This small change in the interface temperature will result in a relatively small change in the brine volume at the interface and the resulting complex permittivity, thereby producing a relatively small change in scattering. A thin snow cover produces the opposite effect - a greater change in interface temperature, brine volume, permittivity, and scattering. This work is extended here to illustrate a variation of this effect over landfast first-year sea ice using in situ measurements of physical snow properties and RADARSAT-1 SAR imagery acquired during the winter of 1999 in the central Canadian Archipelago at cold (~ -26°C) and moderately cold (~ -14°C) snow-sea-ice interface temperatures. We utilize in situ data from five validation sites to demonstrate how the change in microwave scattering covaries and is inversely proportional with the change in the magnitude of SWE. These changes are shown to be detectable over both short (2 days) and longer (45 days) time durations. (Au)

G, F, A, E
Atmospheric temperature; Density; Electrical properties; Fast ice; Physical properties; Remote sensing; Salinity; SAR; Snow; Snow water equivalent; Temperature; Temporal variations; Thermal properties; Thermodynamics; Thickness

G0815
Wellington Channel, Nunavut


Surface-based polarimetric C-band scatterometer for field measurements of sea ice   /   Geldsetzer, T.   Mead, J.B.   Yackel, J.J.   Scharien, R.K.   Howell, S.E.L.
(IEEE transactions on geoscience and remote sensing, v. 45, no. 11, Nov. 2007, p.3405-3416, ill.)
Appendices.
References.
ASTIS record 63293.
Languages: English
Web: doi:10.1109/TGRS.2007.907043
Libraries: ACU

A portable surface-based polarimetric C-band scatterometer for field deployment over sea ice is presented. The scatterometer system, its calibration, signal processing, and near-field correction are described. The near-field correction is shown to be effective for both linear polarized and polarimetric backscatter. Field methods for the scatterometer are described. Sample linear polarized and polarimetric backscatter results are presented for snow-covered first-year sea ice (FYI), multiyear hummock ice, and rough melt pond water on FYI. The magnitude of backscatter signature variability due to system effects is presented, providing the necessary basis for quantitative analysis of field data. (Au)

G, F, A
Electronic data processing; Ice rubble fields; Instruments; Logistics; Measurement; Microwave radiation; Puddles; Radar; Sea ice; Snow

G0815, G0814
Franklin Bay, N.W.T.; Hudson Bay; Resolute Passage, Nunavut


Application of a SeaWinds/QuikSCAT sea ice melt algorithm for assessing melt dynamics in the Canadian Arctic Archipelago   /   Howell, S.E.L.   Tivy, A.   Yackel, J.J.   Scharien, R.K.
(Journal of geophysical research, v.111, no. 7, C07025, July 2006, 21 p., ill., maps)
References.
ASTIS record 63261.
Languages: English
Web: doi:10.1029/2005JC003193
Libraries: ACU

A remotely sensed sea ice melt algorithm utilizing SeaWinds/QuikSCAT (QuikSCAT) data is developed and applied to sea ice [in] the Canadian Arctic Archipelago (CAA) from 2000 to 2004. The extended advanced very high resolution radiometer Polar Pathfinder (APP-x) data set is used to identify spatially coupled relationships between sea ice melt and radiative forcings. In situ data from the Collaborative Interdisciplinary Cryospheric Experiment (C-ICE) (2000, 2001, and 2002) and the Canadian Arctic Shelf Exchange Study (CASES) (2004) are used to validate APP-x data during the melt period. QuikSCAT-detected maps of melt onset, pond onset, and drainage are created from 2000 to 2004, and results indicate considerable interannual variability of melt dynamics within the CAA. In some years, melt stages are positively spatially autocorrelated, whereas other years exhibit a negative or no spatial autocorrelation. QuikSCAT-detected stages of melt are found to be influenced by interannual varying amounts and timing of radiative forcing making prediction difficult. The spatiotemporal variability of ice melt also influences the distribution of ice within the CAA. The lower-latitude regions of the CAA are shown to have accumulated increasing concentrations of multiyear ice from 2000 to 2005. This paper concludes with a discussion of the interplay between thermodynamic and dynamic sea ice processes likely to have contributed to this trend. (Au)

G, D, E, J
Albedo; Atmospheric temperature; Breakup; Canadian Arctic Shelf Exchange Study; Climate change; Collaborative Interdisciplinary Cryospheric Experiment; Effects of climate on ice; Formation; Ice cover; Ice forecasting; Maps; Mathematical models; Measurement; Melting; Microwave radiation; Movement; Numeric databases; Ocean-atmosphere interaction; Radar; Radiation budgets; Remote sensing; Satellites; Sea ice; Seasonal variations; Solar radiation; Spatial distribution; Surface properties; Temporal variations; Thermodynamics; Water content of snow; Winds

G0815, G0813
Canadian Arctic Islands; Canadian Arctic Islands waters; Northwest Passage; Parry Channel, N.W.T./Nunavut


On the utility of SeaWinds/QuikSCAT data for the estimation of the thermodynamic state of first-year sea ice   /   Howell, S.E.L.   Yackel, J.J.   De Abreu, R.   Geldsetzer, T.   Breneman, C.
(IEEE transactions on geoscience and remote sensing, v. 43, no. 6, June 2005, p.1338-1350, ill., maps)
References.
ASTIS record 63277.
Languages: English
Web: doi:10.1109/TGRS.2005.846153
Libraries: ACU

The thermodynamic state of sea ice is important to accurately and remotely monitor in order to provide improved geophysical variable parameterizations in sea ice thermodynamic models. Operationally, monitoring the thermodynamic state of sea ice can facilitate eased ship navigation routing. Sea-Winds/QuikSCAT (QuikSCAT) dual-polarization [i.e., horizontal (HH) and vertical (VV)] active microwave data are available at a sufficiently large spatial scale and high temporal resolution to provide estimates of sea ice thermodynamics. This analysis evaluated the temporal evolution of the backscatter coefficient (sigma°) and VV/HH copolarization ratio from QuikSCAT for estimating sea ice thermodynamics. QuikSCAT estimates were compared against RADARSAT-1 synthetic aperture radar (SAR) imagery and the Canadian Ice Service (CIS) prototype operational ice strength algorithm. In situ data from the Collaborative Interdisciplinary Cryospheric Experiment (C-ICE) for 2000, 2001, and 2002 were used as validation. Results indicate that the temporal evolution of sigma° from QuikSCAT is analogous to RADARSAT-1. The QuikSCAT sigma° temporal evolution has the ability to identify winter, snow melt, and ponding thermodynamic states. Moreover, the copolarization VV/HH ratio of QuikSCAT could provide a second estimate of the ponding state in addition to identifying the drainage state that is difficult to detect by single-polarization SAR. QuikSCAT detected thermodynamic states that were found to be in reasonable agreement to that of in situ observations at the C-ICE camp for all years. Operational implications of this analysis suggest QuikSCAT is a more effective and efficient medium for monitoring ice decay compared to RADARSAT-1 and can be utilized to provide more robust modeled ice strength thresholds. (Au)

G, A, E, L, F, J
Albedo; Atmospheric temperature; Breakup; Canadian Arctic Shelf Exchange Study; Canadian Ice Service; Climate change; Collaborative Interdisciplinary Cryospheric Experiment; Ice cover; Ice forecasting; Ice navigation; Mathematical models; Melting; Meteorology; Microwave radiation; Numeric databases; Puddles; Radar; Radiation budgets; Remote sensing; SAR; Satellites; Sea ice; Seasonal variations; Snowmelt; Solar radiation; Spatial distribution; Strength; Surface properties; Temporal variations; Thermodynamics; Thickness

G0815, G0813
Admiralty Inlet, Nunavut; Barrow Strait, Nunavut; Canadian Arctic Islands; Canadian Arctic Islands waters; Creswell Bay, Nunavut; Griffith Island waters, Nunavut; Lancaster Sound, Nunavut; Lowther Island waters, Nunavut; Northwest Passage; Parry Channel, N.W.T./Nunavut; Peel Sound, Nunavut; Prince Leopold Island waters, Nunavut; Prince Regent Inlet, Nunavut; Wellington Channel, Nunavut


Analysis of surface roughness and morphology of first-year sea ice melt ponds : implications for microwave scattering   /   Scharien, R.K.   Yackel, J.J.
(IEEE transactions on geoscience and remote sensing, v. 43, no. 12, Dec. 2005, p.2927-2939, ill., map)
References.
ASTIS record 63275.
Languages: English
Web: doi:10.1109/TGRS.2005.857896
Libraries: ACU

Variations in wind forcing over summer first-year sea ice (FYI) melt ponds occur at hourly to weekly scales and are a significant contributor to microwave backscatter (sigma°) variability observed from spaceborne synthetic aperture radar (SAR) platforms (e.g., ENVISAT-ASAR and RADARSAT-1). This variability impairs our ability to use SAR to derive information on summer sea ice thermodynamic state and energy balance parameters such as albedo and melt pond fraction. The surface roughness contribution of FYI melt ponds in the Canadian Arctic Archipelago to like-polarized, C-band estimates is analyzed through a spectral and statistical analysis of surface wave height profiles for varying wind speeds, upwind fetch lengths, and melt pond depths. A unique derivation of melt pond surface wave height spectra is presented based on digital video of melt pond surface wave trains. Significant scale surface roughness was observed even at wind speeds of 3 m/s, resulting in small perturbation model estimates of sigma° (HH) ranging from -5 dB at 20° incidence to -22 dB at 50° incidence. Results from a multivariate linear regression analysis show that 53.5% of observed variance in sigma° (HH or VV) can be explained by wind speed, upwind fetch from melt pond edges, and melt pond depth, with no appreciable difference in the relative contribution of explanatory variables. Modeled omnidirectional sigma° as a function of wind speed and incidence angle for 100-m transects collected throughout the melt pond season act to elaborate the role of fetch and depth, as well as the modulating effect of hummocks, on sigma°. (Au)

G, F, E, D, A
Ablation; Albedo; Bathymetry; Clouds; Drainage; Fast ice; Floods; Formation; Mathematical models; Measurement; Mechanical properties; Melting; Microwave radiation; Ocean waves; Ocean-atmosphere interaction; Optical properties; Pack ice; Physical properties; Puddles; Radiation budgets; Salinity; SAR; Satellites; Sea ice; Snow; Snowpatches; Spatial distribution; Surface properties; Temperature; Temporal variations; Thermodynamics; Thickness; Topography; Velocity; Video tapes; Winds

G0815, G0813
McDougall Sound, Nunavut; Truro Island, Nunavut


An evaluation of SeaWinds/QuikSCAT data for the estimation of the decay status of first-year sea ice   /   Howell, S.E.L.   Yackel, J.J.   De Abreu, R.A.   Geldsetzer, T.   Breneman, C.
In: IGARSS 2004 : 2004 IEEE International Geoscience and Remote Sensing Symposium proceedings : science for society : exploring and managing a changing planet, 20-24 September 2004, Anchorage, Alaska. - Piscataway, N.J. : Institute of Electrical and Electronics Engineers, c2004, v. 3, p.2151-2154, ill., maps
References.
Alternate title of proceedings: Science for society : exploring and managing a changing planet.
Alternate title of proceedings: Geoscience and Remote Sensing Symposium, 2004, IGARSS'04, proceedings, 2004 IEEE International.
ASTIS record 64914.
Languages: English
Web: doi:10.1109/IGARSS.2004.1370785
Libraries: ACU

This analysis evaluates the temporal evolution of the microwave backscatter coefficient (sigma°) and VV/HH sigma° co-polarization ratio from Qscat for estimating sea ice thermodynamics. Qscat sigma° were compared against RADARSAT-1 SAR sigma° and in situ data from the Collaborative Interdisciplinary Cryospheric Experiment (C-ICE) for 2000, 2001, and 2002 were used as validation. Results indicate that the temporal evolution of sigma° from Qscat is analogous to RADARSAT-1. The Qscat sigma° temporal evolution has the ability to identify Winter, Snow Melt, and Ponding thermodynamic states. Moreover, the co-polarization VV/HH ratio of Qscat provides a more robust estimate of the Ponding state and identifies the Drainage state that is difficult to detect by single polarization SAR. (Au)

G, F, E, A, L
Breakup; Collaborative Interdisciplinary Cryospheric Experiment; Drainage; Ice cover; Ice forecasting; Marine transportation; Melting; Microwave radiation; Navigational aids; Pack ice; Radar; Remote sensing; SAR; Satellites; Sea ice; Seasonal variations; Snowmelt; Surface properties; Temporal variations; Thermodynamics; Water content of snow; Winds

G0815
Cornwallis Island waters, Nunavut; Parry Channel, N.W.T./Nunavut; Queen Elizabeth Islands waters, N.W.T./Nunavut


A vessel transit assessment of sea ice variability in the western Arctic, 1969-2002 : implications for ship navigation   /   Howell, S.E.L.   Yackel, J.J.
(Canadian journal of remote sensing, v. 30, no. 2, Apr. 2004, p. 205-215, ill., maps)
References.
ASTIS record 63269.
Languages: English
Web: doi:10.5589/m03-062
Libraries: ACU

Recent investigations have shown reduced sea ice extents in Arctic regions and subsequently suggested that the Northwest Passage (NWP) might be able to sustain a prolonged shipping season. To date, no scientific evidence has been presented, within a ship navigation framework, to support increased marine traffic. The Arctic Ice Regime Shipping System (AIRSS) ice numeral (IN), which controls shipping activity in Canadian Arctic waters, was spatially assimilated with the Canadian Ice Service (CIS) historical digital database utilizing a geographic information system (GIS). INs provide a quantifiable framework for examining historical ice states in the context of ship navigation. Results provide a spatial and temporal assessment of ship navigation variability, within a ship transit framework from 1969 to 2002 for the western portion of the NWP. Feasible routes through the NWP experience extreme interannual variability in INs over the past 34 years. Yearly fluctuations of the IN can be attributed to the frequency of multiyear ice (MYI) encounters. The western coast of Banks Island experienced lower INs since 1991 and may be a potential barrier to completely navigating the NWP. Decreases in INs were also found to be associated with the positive signal of the arctic oscillation (AO) index. High-latitude MYI invasions into NWP shipping lanes appear [to] be a major pitfall of future navigation routing in the face of climate warming. (Au)

G, L, E, J, D
Atmospheric circulation; Canadian Ice Service; Climate change; Effects of climate on ice; Geographical positioning systems; Ice control; Ice forecasting; Ice navigation; Marine navigation; Marine transportation; Meteorology; Ocean currents; Ocean temperature; Sea ice; Spatial distribution; Temporal variations; Thermodynamics; Thickness; Water masses; Winds

G07, G0815
Banks Island waters, N.W.T.; Barrow Strait, Nunavut; Canadian Beaufort Sea; M'Clure Strait, N.W.T.; Northwest Passage; Peel Sound, Nunavut; Prince of Wales Strait, N.W.T.; Victoria Strait, Nunavut; Viscount Melville Sound, N.W.T./Nunavut


On the use of synthetic aperture radar (SAR) for estimating the thermodynamic evolution of snow covered first year sea ice   /   Yackel, J.J.   Barber, D.G. [Supervisor]
Winnipeg, Man. : University of Manitoba, 2001.
xxii, 245 p. : ill., maps ; 28 cm.
(ProQuest Dissertations & Theses publication, no. NQ57518)
ISBN 0-612-57518-7
Appendix.
References.
Thesis (Ph.D.) - University of Manitoba, Winnipeg, Man., 2001.
Indexed from a PDF file acquired from ProQuest Dissertations & Theses.
ASTIS record 55375.
Languages: English
Libraries: OONL

The Ocean-Sea Ice-Atmosphere (OSA) boundary operates as a complex and highly coupled system whereby the thermodynamic properties of the system are affected by atmospheric and hydrospheric forcing at a continuum of spatial and temporal scales throughout the annual cycle. In this dissertation I evaluate the seasonal co-relationship between the thermodynamic, mechanical, ablation state and microwave backscatter characteristics of the OSA to provide inter and intra-annual spatio-temporal information on snow covered, landfast smooth first year sea ice (FYI) in the Canadian Arctic during the spring melt period. I present techniques to invert physical and radiative information from this surface using synthetic aperture radar (SAR) data. The research concludes by addressing issues concerning sea ice ablation state forecasting for the purpose of proving strategic marine navigation information. Results show that the bulk thermodynamic properties of smooth FYI can be approximated by time series SAR and that the information can be further exploited to estimate specific characteristics of the thermodynamic state of the system at a particular point in the seasonal evolution. Time series SAR is shown to be associated with evolution and magnitude of specific radiation and energy state variables during the spring melt period. Relationships between microwave scattering and the climate state indicators proved sensitive to the diurnal acquisition times of RADARSAT-1. Time series analyses further demonstrate that RADARSAT-1 ScanSAR data can be utilized to provide spatio-temporal information on spring melt and melt pond onset timing. Furthermore, RADARSAT-1 is shown to be capable of estimating surface wind speed, melt pond fraction and the integrated shortwave albedo over smooth FYI during the melt pond season. (Au)

G, F, E, D, A, L
Ablation; Albedo; Breakup; Diurnal variations; Fast ice; Ice forecasting; Marine navigation; Ocean-atmosphere interaction; Physical properties; Salinity; SAR; Sea ice; Seasonal variations; Snow cover; Snow metamorphism; Snowmelt; Solar radiation; Spatial distribution; Temperature; Temporal variations; Thermal regimes; Thermodynamics; Theses

G0815, G09, G0813, G10
Ellesmere Island, Nunavut; Greenland; Lancaster Sound, Nunavut; North Water Polynya, Baffin Bay; Rosse Bay, Nunavut; Wellington Channel, Nunavut


On the estimation of spring melt in the North Water Polynya using RADARSAT-1   /   Yackel, J.J.   Barber, D.G.   Papakyriakou, T.N.
(Atmosphere-ocean, v. 39, no. 3, Sept. 2001, p. 195-208, ill., maps)
References.
ASTIS record 50613.
Languages: English
Libraries: ACU

This paper evaluates the utility of time series RADARSAT-1 Synthetic Aperture Radar (SAR) to detect melt onset (MO) and pond onset (PO) in the North Water (NOW) Polynya. SAR detected MO was associated with the approach of the daily average near-surface air temperature (Tair) toward freezing, the beginning of a daily average surplus in the net all-wave radiation flux (Q*), and a sharp decrease in the integrated shortwave albedo (alpha) at the surface. Relationships between microwave scattering and air, snow surface and ice surface temperature, up until MO, proved sensitive to the diurnal acquisition times of RADARSAT-1. Time series results demonstrate that, despite its 'uncalibrated' status, RADARSAT-1 ScanSAR data unambiguously identifies MO and PO over landfast First-Year Ice (FYI) within the NOW Polynya. Spatially, results suggest a significantly earlier spring melt on the Greenland coast compared to the Ellesmere coast (10 to 15 days for regions between 77°N and 79°N and up to 45 days for regions between 76°N and 77°N). The regional near-surface air temperature pattern was consistent with the spatial pattern of a SAR detected date of MO and PO. (Au)

G, D, E
Albedo; Atmospheric temperature; Climate change; Energy budgets; Heat budgets; Melting; Ocean-atmosphere interaction; Polynyas; SAR; Sea ice; Snow cover; Solar radiation

G09, G02, G03, G0815
Arctic Ocean; Ellesmere Island waters, Nunavut; Greenland waters; North Water Polynya, Baffin Bay


The physical, radiative and microwave scattering characteristics of melt ponds on Arctic landfast sea ice   /   Barber, D.G.   Yackel, J.J.
(International journal of remote sensing, v. 20, no. 10, 10 July 1999, p.2069-2090, ill., map)
References.
ASTIS record 48766.
Languages: English
Web: doi:10.1080/014311699212353
Libraries: ACU

Melt ponds are an important characteristic of Arctic sea ice because of their control on the surface radiation balance. Little is known about the physical nature of these features and to date there is no operational method for detection of their formation or estimation of their aerial fraction. Coincident in situ observations, aerial surveys and synthetic aperture radar data from a field site in Arctic Canada are compared in an evaluation of the physical, radiative and electrical properties of melt ponds on first-year and multiyear sea ice. Results show that the interrelationships between the thermal diffusivity and conductivity of the snow cover control the mechanisms of snow ablation. Aerial fractions of snow patches, and light and dark coloured melt ponds, show considerable variation both as a function of proximity to land and due to ice type. First-year sea ice is shown to have a water background with discrete snow patches distributed throughout. Multiyear sea ice consists of discrete 'particles' within a snow background. Morphological measurements indicate that snow patches range in size with average areas of from 5 to 20 m². Pond sizes over multiyear sea ice are also highly variable with averages ranging from 15 to 20 m². The integrated shortwave albedo was measured in the field and averaged to: snow patches (0.64 ±0.07); light melt ponds (0.29 ±0.04); and dark melt ponds (0.14 ±0.03). Snow patch size statistics explained a statistically significant proportion of the surface shortwave albedo. We found that microwave scattering could be used to obtain a measure of the onset of melt and had utility in detecting subtle details of the thermodynamic transition from winter through early melt into pond formation. We formalized a statistical relationship between microwave scattering and surface climatological albedo (sigma°-alpha relationship). We found the relationship valid only for landfast first-year sea ice under windy conditions. We conclude with a discussion of the role of surface wind stress and diurnal cycling in specification of the Sigma°-alpha relationship. (Au)

G, E, F
Ablation; Aerial surveys; Albedo; Detection; Electrical properties; Energy budgets; Fast ice; Formation; Measurement; Melting; Ocean-atmosphere interaction; Passive microwave remote sensing; Physical properties; Puddles; Radiation budgets; Remote sensing; SAR; Sea ice; SIMS; Snow; Snowpatches; Solar radiation; Surface properties; Temperature; Thermal properties; Thermodynamics; Winds

G0815, G0813
Cornwallis Island waters, Nunavut; Cornwallis Island, Nunavut; Lowther Island waters, Nunavut; Resolute Passage, Nunavut


Estimating the thermodynamic state of snow covered sea ice using time series synthetic aperture radar (SAR) data   /   Barber, D.G.   Yackel, J.J.   Wolfe, R.L.   Lumsden, W.
In: Proceedings of the Eighth (1998) International Offshore and Polar Engineering Conference, Montréal, Canada, May 24-29, 1998. - [S.l. : The International Society of Offshore and Polar Engineers, 1998?], p. 50-54, ill.
References.
ASTIS record 46250.
Languages: English

Microwave remote sensing of sea ice has traditionally focused on the estimation of dynamic, kinematic, and structural characteristics of the ice surface/volume. Recent evidence shows that the thermodynamic state of sea ice can be estimated using the temporal evolution of the average relative scattering coefficient (Delta sigma 0) measured with a Synthetic Aperture Radar (SAR). This thermodynamic/microwave scattering link has broad implications in ice related engineering (e.g., ice strength estimation) and in ocean-sea ice-atmosphere process studies (e.g., ice-albedo feedback). In this paper we present the theoretical framework required to link the thermodynamics, brine volume and microwave scattering over snow covered sea ice. The principal coupling in this relationship shows that as the temperature of the ice/snow volume increases there is an associated increase in the brine volume. This creates an increase in the complex permittivity (epsilon*) of the volume thereby causing a change in the microwave scattering coefficient (sigma 0). We show how Delta sigma 0 changes as the seasonal evolution of the ice volume progresses from winter through to melt pond formation. We then show how this information can be exploited to estimate various characteristics of the thermodynamic state of the sea ice at a particular point in the seasonal evolution (e.g., winter; onset of melt; pendular and funicular snow regimes; ice decay, etc.). We conclude by reviewing how this time series information may find utility within the Arctic Ice Regime Shipping System (AIRSS). (Au)

G, F, M
Energy budgets; Ice forecasting; Ice navigation; Microwave radiation; Ocean engineering; Passive microwave remote sensing; Salinity; SAR; Sea ice; SIMS; Snow; Temperature; Thermodynamics

G0815
Resolute Bay, Nunavut


Geophysics, dielectrics and emissivities and their relationship to snow water equivalence (SWE) estimation using SSM/I data   /   Yackel, J.J.   Barber, D.G.   Drobot, S.D.
Winnipeg, Man. : Centre for Earth Observation Science, University of Manitoba, 1996.
1 v.
(CEOSTEC-96-3- 1)
References.
Not seen by ASTIS. Citation from NSTP.
ASTIS record 43175.
Languages: English

Snow is a significant and vital component of the hydrological cycle in the temperate regions of the Northern Hemisphere and therefore must be examined in any detailed study of climate change or hydrosphere-biosphere interactions. The water equivalent of snow on the ground, or snow water equivalent (SWE), is the depth of water resulting from a melt of a column of snow cover and is important for understanding spring moisture recharge contributions for crop growth and river stage forecasting. Because of the widespread extent of snow cover in the Northern Hemisphere, satellite borne passive microwave remote sensing systems offer the optimal spatial and temporal coverage necessary for operational snow water equivalence mapping. ... Work by previous researchers ... has consistently linked imprecisions in snow water equivalence (SWE) mapping to spatial and temporal heterogeneties in the complex dielectric constant and volume emissivity of snow covered surfaces. In this work we propose to: 1) provide a theoretical review of the linkages between snow geophysics, electrical properties and the emissivity of a naturally occuring snow cover; and 2) to evaluate these models within the context of SWE mapping using passive microwave remote sensing over a site where detailed snow course information is maintained throughout an annual cycle. ... (Au)

F
Electrical properties; Mapping; Ocean-atmosphere interaction; Satellites; Snow; Snow hydrology; Snow water equivalent; Spatial distribution; Special Sensor Microwave/Imager

G01
Polar regions


Seasonal evolution of passive microwave signatures on snow covered firstyear sea ice   /   Drobot, S.D.   Barber, D.G.   Yackel, J.J.
Winnipeg, Man. : Centre for Earth Observation Science, University of Manitoba, 1996.
1 v.
(CEOSTEC-96-3- 2)
References.
Not seen by ASTIS. Citation from NSTP.
ASTIS record 43174.
Languages: English

The objectives of this experiment are to link the seasonal evolution of passive microwave radiometer signatures to microscale physical and electrical properties of the snow cover, as well as aspects of the surface energy balance. This project will allow analysis of SIMMS'95 in situ radiometer observations relative to surface energy fluxes between April and June (spring transition). Specifically, this project will: i - Monitor the seasonal evolution of (i) snow and ice properties; (ii) climate variables, and (iii) passive microwave radiometer signatures. ii - Investigate the statistical interrelationships amongst items i, ii, and iii of point 1, above. In this research, snow and ice properties collected include temperature, snow density, snow salinity, and snow wetness; photosynthetically active radiation (PAR) and reflective shortwave (K up) represent the climatological measurements; and brightness temperatures were collected in V and H polarizations. ... (Au)

G, E, F
Electrical properties; Energy budgets; Meteorology; Ocean-atmosphere interaction; Passive microwave remote sensing; Physical properties; Sea ice; SIMMS; Snow; Snow hydrology; Thermodynamics

G01
Polar regions


C-ICE 96 field summary   /   Drobot, S.D. [Editor]   Yackel, J.J. [Editor]   Barber, D.G.
Winnipeg, Man. : Centre for Earth Observation Science, University of Manitoba, 1996.
1 v.
(CEOSTEC-96-9- 1)
Appendices.
Not seen by ASTIS. Citation from NSTP.
ASTIS record 43173.
Languages: English

The Collaborative Interdisciplinary Cryospheric Experiment (C-ICE) is a multi-year field experiment that has many individual projects, each with autonomous goals and objectives. The science conducted has either directly evolved from research relating to one of four general themes: i) sea ice energy balance; ii) numerical modelling of atmospheric processes; iii) remote sensing of snow covered sea ice; and iv) ecosystem studies. ... The C-ICE field program provides the surface data required to develop an understanding of the process linkages operating in an environment typical of fast ice conditions in the Canadian Arctic Archipelago. A modelling component within C-ICE operates in conjunction with the field activities, although the modelling aspects will assume greater importance as the existing field data are analyzed. The principal objective of this subgroup is to integrate the field data within numerical models of the primary processes operating in our area of interest, for the expressed purpose of 'scaling up' observations to more regional scales. ... (Au)

G, F, E
Atmospheric temperature; Clouds; Collaborative Interdisciplinary Cryospheric Experiment; Effects of ice on climate; Energy budgets; Mathematical models; Meteorology; Microclimatology; Microwave radiation; Ocean-atmosphere interaction; Passive microwave remote sensing; Remote sensing; Sea ice; Snow; Snow hydrology; Solar radiation; Surface properties; Temperature; Weather stations; Winds

G081
Canadian Arctic waters


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