Melt Duration Variability and Sea Ice Conditions within the Canadian Arctic Archipelago: 1979-2007

The links between melt duration and sea ice conditions within the Canadian Arctic Archipelago (CAA) and its sub-regions were explored from 1979 to 2007. Melt duration was derived from passive microwave brightness temperatures and sea ice conditions were extracted from the Canadian Ice Service Digital Archive. Melt duration in the CAA is increasing at 6.0 days decade-1 which is statistically significant at the 99 percent confidence level. The longest melt durations within the CAA were 1998 (123 days), 2006 (118 days), and 1994 (115 days). All sub-regions within the CAA also exhibited positive slopes for melt duration and only the Western Arctic Waterway was not statistically significant. Minimum sea ice coverage with the CAA has decreased by -2.42x103km2year-1 (-6.6 percent decade-1) but this trend has yet to reach statistical significance at the 90 percent confidence level. The years with the minimum sea ice coverage within the CAA were 1998 (131x103km2), 2007 (169x103km2), and 1999 (216x103km2). All sub-regions within the CAA are experiencing negative slopes in sea ice coverage but only Baffin Inlet is statistically significant at the 95 percent confidence level. Results however show a clear shift between decreases in the amount of first-year ice promoted to multi-year ice (- 1.67x103km2year-1) within the CAA compared to increases in the amount of multi-year ice imported into the CAA (2.04x103km2year-1). Longer melt seasons within the CAA may not yet bring about substantial reductions sea ice conditions because the CAA acts as a drain-trap for multi-year ice. As the melt season length continues to increase, and the transition to a summer-time sea ice free Arctic continues, the supply of multi-year ice from the Arctic Ocean to the CAA may reduce but it is unlikely to stop. With respect to practical utilization of the Northwest Passage it is apparent that as the seasonal ice breaks-up earlier, multi-year ice then begins to flow and fill the open water gaps resulting in only a minor lengthening of the shipping season.