Variability of Arctic climate and sea ice over the past millennium: implications for ice cap mass balance

Sea level pressure over the Arctic has decreased dramatically, signifying an anomalous circulation within the atmosphere (Walsh et al., 1996). The Arctic Atlantic Layer (200-500m depth) has warmed by about 1.5ºC (Carmack et al., 1995), perhaps contributing to a reduction in the thickness of sea ice within the Arctic Basin (Rothrock et al., 1999). Sea ice extent has decreased at both regional and hemispheric scales (Parkinson et al., 1999). Ice cap mass balance in the Canadian Arctic has been persistently negative since ~1960, contributing as much as 2mm to global sea level rise over that period.

Variability in climate, sea ice concentration and transport, observed at both regional and pan-Arctic scales has important consequences for the rate and pattern of freshwater export from the Arctic, processes of deep-water formation in the North Atlantic region, marine biological productivity, and ice cap mass balance.

It has been suggested that this variability is now being excited by anthropogenic forcing on the climate system. Several modeling studies predict that this may result in an Arctic that is largely ice-free in summer by the end of the 21st century (Walsh and Timlin, 2003; Johannessen et al., 2004). This would have profound implications for marine ecosystems, navigation in Arctic waters (Alt et. al., 1985), and the traditional lifestyles of aboriginal peoples within the region.