Cryospheric and Polar Processes Seminar

Variability, Trends, and Predictability of Seasonal Sea Ice Retreat and Advance in the Chukchi Sea
by Dr. Mark Serreze, Director - National Snow and Ice Data Center, CIRES Fellow & Professor in Geography, University of Colorado
Continued summer sea ice loss will make the Arctic Ocean increasingly accessible.  There is hence a need for a better understanding not only of the evolution of the sea ice cover on decadal and longer scales, but on seasonal time scales that bear directly on economic activities. Predicting the seasonal onset and duration of open water on a regional basis is of particular importance, and the Chukchi Sea stands out in this regard.  This shallow shelf sea, which has seen some of the sharpest downward trends in September ice extent over the satellite record, is a focus of resource exploration, and vessels transiting the Arctic Ocean must invariably pass through it. The Chukchi Sea is also part of the seasonal migration route for bowhead whales that supports subsistence hunting.  An analysis of de-trended time series reveals that 68% of the variance in the date at which sea ice in the Chukchi Sea retreats to the continental shelf break in spring and summer can be explained simply by the April through June Bering Strait heat inflow.  In turn,  67% of the variance in the date at which ice advances back to the shelf break in autumn and winter can be explained by the combination of the July through September Bering Strait heat inflow and the date of ice retreat.  The link with the retreat date is that early ice retreat enables a longer period of seasonal heat uptake in the ocean mixed layer, meaning that more heat must be lost to the atmosphere before ice can form.  Developing an operational prediction scheme for seasonal retreat and advance in the Chukchi Sea would require more timely acquisition of Bering Strait heat inflow data than is presently possible. Predictability will likely always be limited by the chaotic nature of atmospheric circulation patterns.