Percent per decade changes in multi-year ice and all ice types in the Marine Arctic Ecozones. 2010 Canadian Marine Ecosystem Status and Trends Report

Between 1979 and 2008, first-year sea ice in the summer has been declining at a rate of 8.7% per decade, whereas the thick multi-year sea ice in the summer is being lost at an average rate of 6.4% per decade and over 20% per decade in some areas of the Canadian Arctic Archipelago. This decreasing trend in multi-year sea ice may be counteracted by the import of multi-year ice from the Arctic Ocean, or sustained by longer melt seasons that limit the promotion of first-year to multi-year sea ice. However, both of these factors have declined in recent years. Between 1979 and 2008 in the CAA, the longest melt season occurred in 2008 and there was a significant increasing trend in melt season duration (i.e., 7 days/decade).

Canadian Science Advisory Secretariat Science Advisory Report 2010/030, 2010 Canadian Marine Ecosystem Status and Trends Report [pdf], July 2010