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Bottomfast sea ice is an integral part of many near-coastal Arctic ecosystems with implications for subsea permafrost, coastal stability and morphology. Bottomfast sea ice is also of great relevance to over-ice travel by coastal communities, industrial ice roads, and marine habitats. There are currently large uncertainties around where and how much bottomfast ice is present in the Arctic due to the lack of effective approaches for detecting bottomfast sea ice on large spatial scales. Here, we suggest a robust method capable of detecting bottomfast sea ice using spaceborne synthetic aperture radar interferometry. This approach is used to discriminate between slowly deforming floating ice and completely stationary bottomfast ice based on the interferometric phase. We validate the approach over freshwater ice in the Mackenzie Delta, Canada, and over sea ice in the Colville Delta and Elson Lagoon, Alaska. For these areas, bottomfast ice, as interpreted from the interferometric phase, shows high correlation with local bathymetry and in-situ ice auger and ground penetrating radar measurements. The technique is further used to track the seasonal evolution of bottomfast ice in the Kasegaluk Lagoon, Alaska, by identifying freeze-up progression and areas of liquid water throughout winter.

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This open file reports on recent geoscience data collected and monitoring sites installed by the Geological Survey of Canada (GSC) in collaboration with Aboriginal Affairs and Northern Development Canada (AANDC), Northwest Territories Geoscience Office (NTGO), Government of the Northwest Territories (GNWT) Environment and Natural Resources (ENR) and the Department of Transport (DOT), BGC Engineering Inc., Carleton University, and the University of Ottawa. The report represents the first of several co-published GSC / NTGO Open File reports under the Climate Change Geoscience Program. A 2010-11 field program under the Transportation Risk in the Arctic to Climatic Sensitivity (TRACS) activity in the Climate Change Geoscience Program included extensive fieldwork in the Yellowknife area between June and September, 2010. Field data collection by the Geological Survey of Canada and Carleton University included 14 CRREL-cored boreholes and ecological descriptions at 48 sites. An additional 20 ecological site descriptions were made by University of Ottawa students. Collaborative work with BGC Engineering Inc. included field observations and soil analysis (grain size and Atterberg limits) at test pits along Highway 3, and 15 water-jet drilled holes for subsequent temperature cable installations. Numerous temperature measurement sites were also established with AANDC along a 170 km transect between Behchoko and Tibbitt Lake including six air temperature sites, six multi-channel near-surface temperature sites and seven water temperature sites. In March 2011, additional field data were collected including snow depths at 45 sites, densities at 18 sites, and ice thicknesses at eight pond sites. Snow depth transect surveys were also conducted at 11 sites along Highway 3, across the highway embankments and right-of-ways. These data were collected in order to provide baseline information regarding the nature and properties of permafrost in the Yellowknife area.

Interannual changes in seasonal ground freezing and near‐surface heat flow beneath zones of bottom‐fast ice (BFI) were examined over the winters of 2005–06 and 2006–07 within the near‐shore zone of the Mackenzie Delta, Canada. Winter variability in ground thermal conditions was determined at three monitoring sites. Ground‐penetrating radar surveys were conducted in late winter to determine spatial variability in landfast ice conditions and the extent of ice‐bonded sediments. Shallow water sites (<0.5 m‐water depth) were characterised by early onset of BFI, freezeback of the active layer and mean winter sediment bed temperatures ranging between −3°C and −10°C. In contrast, deep water sites (>1 m of water) experienced prolonged periods of floating ice, which limited the duration of ice contact with the sediment bed and the depth of seasonal frost, and resulted in warmer winter ground temperatures (between −0.5°C and −2.6°C). Under similar water depths, interannual changes in ice growth altered the timing of BFI and winter heat loss from the ground. When comparing conditions over the two winters, 2005–06 was characterised by a decrease in ice thickness that limited the extent of BFI and seasonal cooling of the ground. These changes in ice conditions had a greater effect on the thermal conditions at sites where water depths were close to the maximum ice thickness. The short ice contact times at these sites are important to the thermal state of permafrost, as only minimal heat exchange contributing to permafrost cooling occurs prior to freezeback of the active layer. Copyright © 2010 John Wiley & Sons, Ltd.