Sea Ice Evolution in the Pacific Arctic by Selected CMIP5 Models: the Present and the Future

With fast declining of sea ice cover in the Arctic, the timing of sea ice break-up and freeze-up is an urgent economic, social and scientific issue. Based on daily sea ice concentration data we assess three parameters: the dates of sea ice break-up and freeze-up and the annual sea ice duration in the Pacific Arctic. The sea ice duration is shrinking, with the largest trend during the past decade (1990-2015); this declining trend will continue based on CMIP5 model projections. The seven CMIP5 models used in current study are able to simulate all three parameters well when compared with observations. Comparisons made at eight Chukchi Sea mooring sites and the eight Distributed Biological Observatory (DBO) boxes show consistent results as well. The 30-year averaged trend for annual sea ice duration is projected to be -0.68 days/year to -1.2 days/year for 2015-2044. This is equivalent 20 to 36 days reduction in the annual sea ice duration. A similar magnitude of the negative trend is also found at all eight DBO boxes. The reduction in annual sea ice duration will include both earlier break-up dates and later freeze-up date. However, models project that a later freeze-up contributes more than early break-up to the overall shortening of annual sea ice duration. Around the Bering Strait future changes are the smallest, with less than 20-days change in duration during next 30 years. Upto 60 days reduction of the sea ice duration is projected for the decade of 2030-2044 in the East Siberia, the Chukchi and the Beaufort Seas.