Arctic is shrinking in all seasons , but most significantly during summer . River and lake ice , and permafrost , seasonally frozen ground are reduced . The melting ice caps , glaciers and ice sheets to the rising sea level is approximately 1 .2 - 0 .4 mm per year for the period 1993 - 2003 (IPCC , 2007b . The maximum areal extent of seasonally frozen ground in the northern hemisphere has shrunk by 7 since 1990 (IPCC , 2007a . Montana 's Glacier National Park of 150 glaciers in...











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