The largest ice shelf in the Arctic has broken, and scientists who have studied it closely say it is evidence of ongoing and accelerated climate change in the north polar region. The Ward Hunt Ice Shelf is located on the north coast of Ellesmere Island in Canadas Nunavut territory and its northernmost national park. This ancient feature of thick ice floating on the sea began forming some 4,500 years ago and has been in place for at least 3,000 years.
Warwick Vincent and Derek Mueller of Laval University in Quebec City, Quebec, and Martin Jeffries of the University of Alaska Fairbanks have studied the Ward Hunt Ice Shelf on site and through RADARSAT imagery and helicopter overflights. They report in the journal Geophysical Research Letters that a three decade long decline in the Ward Hunt Ice Shelf culminated in its sudden break-up between 2000 and 2002. It fragmented into two main parts with many additional fissures. It also calved a number of ice islands, some of which are large enough to pose a danger to shipping and to drilling platforms in the Beaufort Sea.
An immediate consequence of the ice shelfs rupture was the loss of almost all of the freshwater from the northern hemispheres largest epishelf lake, which had been dammed behind it in 30 kilometer [20 mile] long Disraeli Fiord. An epishelf lake is a body of mostly freshwater trapped behind an ice shelf. The freshwater layer in the Disraeli Fiord measured 43 meters [140 feet] in depth and lay atop 360 meters [1,200 feet] of denser ocean water. The loss of fresh and brackish water has affected a previously reported unique biological community, consisting of both freshwater and marine species of plankton. The breakup of the ice shelf has also reduced the habitat available for cold-tolerant communities of microscopic animals and algae that live on the upper ice surface.
Harvey Leifert | AGU
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