Sea ice thickness variability in the Canadian Beaufort Sea

Abstract:

Sea ice in the Canadian Beaufort Sea has retreated strongly in recent summers, raising interest in its role for the Arctic climate and eco system, and in allowing access for shipping and offshore resources extraction both in Canada and in Alaskan waters further downstream. However, little is known about the thickness of its first- and multiyear ice regimes at the end of winter which are important in preconditioning the ice cover for summer retreat. Here we present results from spring-time airborne electromagnetic ice thickness surveys performed since 2009 over hundreds of kilometers of various first- and multiyear ice regimes. Surveys are complemented by satellite radar imagery allowing regional extrapolation of results. Results show large regional thickness variability with bands of first-year ice in the south and east, of heavily deformed old multiyear ice further north, and of younger multiyear ice in the Canada Basin further to the Northwest. This regional variability is hard to capture with moored ice thickness echo sounders. While the regions of multiyear ice have become thinner overall, there is little evidence for thinning of first-year ice despite later fall freeze-up. This may be related to a thinner snow cover and supports hypotheses about the resilience of first-year ice in a warmer Arctic. Due to the spatial extent of the surveys our data provide unique opportunities for the validation of satellite and airborne radar and laser altimeter and microwave radiometer ice thickness retrievals for which we will show a few examples. We have also analysed the occurrence of extreme ice features and hummock fields and show that these occur frequently both in the first- and multiyear ice regimes. These continue to pose hazards for marine infrastructure.