Ice shelf losses in the Canadian High Arctic, 2005-2010

The total area of the remaining Canadian ice shelves has decreased from 1043 km2 in July 2005 to ~650 km2 in September 2010. This decrease includes the complete loss of the Ayles Ice Shelf in 2005 and the Markham Ice Shelf in 2008, and substantial losses to the Serson and Ward Hunt Ice Shelves since 2008. These losses are consistent with other changes to multiyear sea ice features and extent in this region, and have resulted in many fiords along northern Ellesmere Island becoming ice free for the first time in ~5000 years. Satellite image analysis of the recent ice shelf breakup events indicates that these losses have resulted from calving at both their frontal margins into the Arctic Ocean, and at their rearward margins into their own fiords (e.g., Ward Hunt). The rearward calving is possible because: (1) the glaciers which once supplied these ice shelves have now retreated up the fiords, and/or (2) the epishelf lake ice which once provided a permanent ice cover over these fiords now melts on a seasonal basis. This makes these ice shelves more vulnerable to losses than typical Antarctic ice shelves which only calve at their frontal margins. Calving at the frontal margins of Ellesmere Island ice shelves is strongly dependent on the presence of late-summer open water leads that develop between the Arctic Ocean pack ice and the coast during offshore wind events. The pack ice normally protects the ice shelf fronts from the effects of wind and waves, and the onshore pressure from the pack ice helps to stabilize them. Recent significant calving events have all occurred during periods where open water leads existed (e.g., losses of >200 km2 of ice shelf occurred during a month-long period of open water in summer 2008). Climate reanalysis of northern Ellesmere Island, and climate records from Eureka, indicate that surface warming has occurred in this region over the past ~50 years, with most warming focused in the winter (at rates of up to 1°C per decade).