12. Recent Changes in Sea Ice Plugs Along the Northern Canadian Arctic Archipelago

For most of the twentieth century, multiyear landfast sea ice (MLSI) existed in semi-permanent plugs across Nansen Sound and Sverdrup Channel in the northern Queen Elizabeth Islands (QEI), Canada. Between 1961 and 2004, these ice plugs only experienced simultaneous break-ups in 1962 and 1998. However, break-ups of both ice plugs have occurred in 9 out of the 12 years since 2005, indicating that these features are not reforming. The history of these plugs is reviewed using Canadian Ice Service ice charts, satellite imagery and a literature review. The weather systems associated with plug break-up events are related to the synoptic patterns defined by Alt (Atmos-Ocean 3:181–199, 1979). Most break-ups occur during Type III synoptic conditions, when a low 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. Ice plug break-ups are also associated with reductions in sea ice concentration along the northwest coast of Ellesmere Island. The removal of these MLSI plugs in recent years aligns with ice shelf losses and reductions in age and thickness of sea ice in the Canadian Arctic Archipelago, with implications for ice import and export through these channels and the response of Arctic sea ice to a changing climate.