| For most of the 20th century, multiyear landfast sea ice (MLSI) existed in semi-permanent plugs across Nansen Sound and Sverdrup Channel and formed an incipient ice shelf in Yelverton Bay, Ellesmere Island in the northern CAA. Both plugs broke in 1962 and 1998, and several breakups within the last decade indicate that the plugs are becoming temporary seasonal features. The history of the plugs is reviewed using Canadian Ice Service ice charts, satellite imagery and a literature review. The weather systems associated with plug breakup events are related to a sequence of synoptic patterns, with most breakups occurring when low pressure centers over the Asian side of the Arctic Ocean and a warm pressure ridge develops over the QEI, creating warm temperatures, clear skies, and frequent wind reversals. The 2005 simultaneous breakup of the plugs was accompanied by the removal of 690 km2 of 55-60 year old MLSI from Yelverton Bay. Ground Penetrating Radar (GPR) and ice cores taken in June 2009 provide the first detailed assessment of the remaining MLSI in Yelverton Inlet, which in turn provides ground-truthing of satellite scenes and air photos used to chart historical changes in the MLSI. The last of the Yelverton Bay MLSI was removed in August 2010. The removal of these MLSI features in recent years aligns with the larger trend of reductions in age and thickness of sea ice in the Canadian Arctic Archipelago. |
