Canadian Ice Service Digital Archive: Trends and Variability 1968-2008

The Canadian Ice Service (CIS) Digital Archive (CISDA) is a compilation of the weekly operational Regional Ice Charts that cover Canadian waters. During the IPY, the data (1968 to present) was made available to the public on the CIS website and the archive was extended and improved by the addition of the climatological Historical Ice Charts. This study identifies trends and variability in ice concentration from CISDA. Prior to the analysis, the quality of the data was assessed by first quantifying errors in the estimates of ice concentration and ice type, and then by identifying any potential bias in estimates by comparing the data with other sea ice data sets. The data revealed that between 1968 and 2008, summer sea ice cover has decreased by -8.9% ± 3.1% decade-1 in Hudson Bay, -2.9% ± 1.2% decade-1 in the Canadian Arctic Archipelago, -8.9% ± 3.1% decade-1 in Baffin Bay, and -5.2% ± 2.4% decade-1 in the Beaufort Sea. In general, these reductions in sea ice cover are explained by increases in early summer surface air temperature (SAT). Within the Canadian Arctic Archipelago and Baffin Bay, the El Ni±o–Southern Oscillation (ENSO) index correlates well with multi-year ice coverage (positive correlation) and first-year ice coverage (negative correlation) suggesting that El Nino episodes precede summers with more multi-year ice and less first-year ice.