Sea ice has a profound effect on wildlife and people who live and hunt in the Arctic. The sea ice also plays a crucial role in global climate system, because of its role in maintaining the global heat balance and its affect on the global ocean thermohaline circulation. Arctic sea ice extent and thickness have decreased dramatically in the 1990’s. The decline of the Arctic sea ice pack may be attributed to the observed increase in surface temperature, but it may also be caused by a simple shift in the winds over the Arctic Ocean such that the older, thicker sea ice is exported from the Arctic Ocean to the warmer waters of the North Atlantic.

In this dissertation, a hypothesis is advanced that the decline of arctic sea ice pack was dynamically induced by changes in the surface winds over the Arctic Ocean. Using a simple model, it is shown that the areal coverage of thick, multi-year ice decreased precipitously during 1989-1990 when the Arctic Oscillation was in an extreme “high index” state, and has remained low since that time. Under these conditions younger sea ice recirculates back to the Alaskan coast more quickly, decreasing the time that new ice has to ridge and thicken before returning for another melt season. During the 2002 and 2003 summers this anomalously young, thin sea ice was advected into Alaskan coastal waters where extensive melting was observed, even though temperatures were locally colder than normal. We show that changes in sea ice driven by variations in wind related to the Arctic Oscillation appear to be the primary factor forcing the observed decreases in sea ice thickness, and thus the increases in surface air temperature and the decreases in sea ice extent that have been observed since 1989. Dynamically induced variations in the age of sea ice explain more than half of the variance in summer sea ice extent.


A PDF of this dissertation can be obtained from http://iabp.apl.washington.edu/Dissertation/.