Changes predicted by the Community Atmospheric Model version 3 (CAM3) 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 1000 hPa geopotential height (Z1000) 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 Z1000 in this region. With reduced sea ice, Z1000 increases over Siberia and is found to be the result of increases in the frequency of strong high-pressure ridges. Increases over the Greenland and Norwegian Seas are 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.