ABSTRACT:

Over the past decade there have been dramatic reductions in the areal extent of sea ice in late summer over the Arctic Ocean. For sub-regions in the western Beaufort Sea (off Alaska) and the deeper offshore waters of the Canadian sector of the Beaufort Sea, the trend towards reduced total ice concentrations in late summer ranges from −11.4 and −7.3% per decade, respectively, which is comparable to the reduction of −11.1% per decade in overall Arctic Ocean during late summer. In the central Canadian Arctic sub-regions through the Northwest Passage, the trends in total ice reduction are smaller at +1 to −6 percent per decade. The trends computed for old ice can be quite different from that of total ice concentrations. In the western "chokepoint" area of the Northwest Passage (Viscount Melville Sound), the late summer trend is −6% per decade and +2.5% per decade for total and old ice, respectively. The trends in the long-term sea-ice thickness measurements in the Beaufort Sea over the continental shelf and in the eastern portions of the Canadian Arctic do not show major reductions unlike measurements from the deepwater Arctic Ocean.

INTRODUCTION

Over the past decade there have been dramatic reductions in the areal extent of sea ice in late summer over the Arctic Ocean. In this paper, we consider the sea ice and related conditions along the Northwest Passage of the Western Arctic Ocean. The Northwest Passage connects the Bering Strait entrance/exit to the Arctic in the west to Baffin Bay in the east. Potential chokepoints for shipping along the Passage include the entrance to the Arctic Ocean itself off Barrow Alaska and the interior portions of the Canadian Arctic Islands, most notably Viscount Melville Sound along the deeper northern branch, and M'Clintock Channel along the shallower southern branch.

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