Impacts of reduced sea ice on winter Arctic atmospheric circulation, precipitation, and temperature

Changes predicted by the Community Climate System Model in winter Arctic atmospheric circulation, precipitation and temperature due to projected reductions in sea ice are investigated from a synoptic climatology perspective using the self-organizing map (SOM) technique. A decrease in geopotential height over Alaska and northern North America is found to be a result of an increase in frequency of patterns with low pressure over much of the Arctic basin. Over Alaska in particular, a deepening of Aleutian lows is also found to contribute to lower geopotential height in this region. With reduced sea ice, geopotential height increases over Siberia and is found to be the result of increases in high geopotential associated with strong high pressure systems. Increased geopotential height over the Greenland and Norwegian Seas is found to be the result of decreases in frequency of strong Icelandic low cyclones. Large increases in precipitation across the Arctic are found to be primarily due to thermodynamic changes, such as increased moisture in the atmosphere, rather than changes in the frequency of cyclones. Temperature changes for the winter season are found to be due almost equally to diabatic heating and changes in temperature advection.