Atmospheric and land surface response to reduced Arctic sea ice extent

With the Arctic climate system changing at unprecedented rates and sea ice extent at near-record lows, an improved understanding of the relationship between sea ice and climate system components is warranted. In a series of model downscaling experiments using present day and projected end of 21 st century sea ice extent, the direct impact of sea ice on the Arctic atmosphere and land surface is examined.;Using the Community Atmospheric Model (CAM), future projections of reduced sea ice are found to result in a decrease in sea level pressure (SLP) across northern North American and the central Arctic and an increase in SLP across much of Siberia in winter. The self-organizing map (SOM) technique is used to understand these mean changes from a synoptic climatology perspective. The decreases seen in SLP are found to be the result of an increased frequency of strong Arctic cyclones and an increased intensity of Aleutian lows, while the strengthened Siberian high is due to an increased frequency of a several synoptic scale patterns with strong high-pressure ridges.;With a reduction in sea ice, precipitation increases significantly throughout the Arctic due almost entirely to higher levels of atmospheric moisture rather than increased cyclone frequency. In addition, very large increases in winter near-surface atmospheric temperature are simulated, and approximately half of the temperature change can be attributed to advection and half to diabatic heating.;The Weather and Research Forecasting Model (WRF) is then forced with lateral boundary conditions from the CAM experiments to examine the land surface response to future sea ice projections across the North Slope of Alaska. Despite warmer near-surface atmospheric temperatures, it is found that spring melt is delayed throughout much of the North Slope due to increased snow pack, and the growing season length is shortened. Increased snow pack in the future sea ice scenario results in warmer soil temperatures for most seasons. However, in the summer soil temperatures are reduced due to increased albedo. These changes imply that sea ice extent acts as a negative feedback on Arctic vegetation growth and have implications for the terrestrial carbon budget.