2.2 Snow cover

Snow cover extent has declined about 10% over the past 30 years, (ACIA 2006) especially in spring and summer. Declines are mostly in the Northern Hemisphere (AMAP 2012). In the Southern Hemisphere, the few long records available show either decreases or no change in the past 40 years or more. (IPCC 2008) Spring peak river flows have been occurring 1-2 weeks earlier during the last 65 years and there is also evidence for an increase in winter base flow in northern Eurasia and North America. (IPCC 2007).

Simulations project widespread reductions in snow cover throughout the 21st century, despite some projected increases at higher altitudes (Walsh 1995) which would lead to redistribution of ecosystems. (Daimaru and Taoda 2004). In general, the snow accumulation season is projected to begin later, the melting season to begin earlier, and the fractional snow coverage to decrease during the snow season. (IPCC 2008; AMAP 2012).

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