Mechanisms in the Development of Anomalous Sea Ice Extent in the Western Arctic: A Case Study

Sea ice is an integral component of the Arctic climate system, forced by and modulating in turn atmospheric and oceanic processes and circulations. The sea ice albedo feedback effect is a dominant factor in the amplification of climate change in the Arctic. Further, sea ice plays an important role in atmosphere-ocean exchanges of heat and momentum, and strongly impacts the upper ocean stratification. Hence, recent changes in Arctic sea ice extent, thickness and concentration have the potential to impact Arctic and global climate profoundly. Further, this complex interactive system presents a major challenge in coupled models of Arctic climate.

An overall decreasing trend of about 3% per decade in sea ice extent has been inferred from satellite passive-microwave data over the past two decades, but this overall trend masks a high degree of spatial, interannual and interseasonal variability in sea ice changes. Arctic sea ice extent exhibited a record minimum extent during the September of 1990, dominated by a rapid retreat in the Chukchi, East Siberian and Laptev Seas. It has been hypothesized that the observed warm spring and summer air masses from the Arctic coast were able to penetrate far over the Arctic Ocean, melting some sea ice and driving much of the remainder away from the shore and towards the central ice pack. However, similar atmospheric conditions were noted for the Beaufort Sea, which did not experience anomalous ice retreat at this time. In 1998, these conditions did yield a strong ice retreat in the Beaufort Sea. The work presented here is intended to diagnose, using a coupled atmosphere-ice regional climate model, the mechanisms which may be important in the creation of regional sea ice anomalies.