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October 27, 2003
Seattle, Washington, USA

Drivers and Causes of Arctic Environmental Change

Mark C. Serreze^1
1Cooperative Institute for Research in Environmental Sciences, University of Colorado, Campus Box 449, Boulder, CO, 80309-0449, USA, Phone 303-492-2963, Fax 303-492-2468, serreze@kryos.colorado.edu

Of the various environmental changes that have been observed over Northern high latitudes in recent decades, the most obvious are pronounced rises in winter and spring surface air temperature over sub-Arctic land areas, reductions in sea ice extent and thickness, and warming and increased areal extent of the Arctic Ocean's Atlantic layer. Other studies point to increased river discharge, regional changes in precipitation, warming of soils and permafrost, increased shrubbiness and altered cloud cover. For many of these changes, there is overwhelming evidence of strong links with increasing dominance of the positive phases of the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO). The AO/NAO are natural modes of atmospheric variability and there is debate as to whether they are separate phenomena. Some modeling studies point to the recent AO/NAO trend as a reflection of inter-decadal climate variability. Other studies lend credence to the view that it is unusual and may be a response to changes in greenhouse gases.

Although the AO/NAO provides a useful coordinating framework, linkages with many aspects of change appear to be complex, indirect or weak. For example, AO/NAO links with precipitation and net precipitation over the major Eurasian watersheds that could help explain changes in annual river discharge are not especially strong. Part of the problem may be the inherent difficulty in accurately measuring precipitation. There have been notable increases in winter discharge from the Yenisey and Lena. There is some evidence of a link with changes in ground ice and active layer depth. On the other hand, recent work has shown that the direct human effects of diversions and impoundments are significant. While there is a demonstrated relationship between the winter AO and subsequent summer sea ice conditions, variability in the summer circulation is also important. A good case study is provided by the record low sea ice conditions observed in 2002. Some changes, such as in cloud cover, are puzzling. It appears that while Arctic cloud cover has decreased during winter, it has increased during summer.

Abstract Categories: Keynote, Drivers and Causes

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