Observing and interpreting the seasonal variability of the oceanographic fluxes passing through Lancaster Sound of the Canadian Arctic Archipelago

Abstract

As part of the Arctic/Sub-Arctic Ocean Flux (ASOF) and the International Polar Year (IPY) programs, a research project consisting of mooring and analysis work has studied the ocean and ice fluxes passing through Lancaster Sound, one of the three main pathways through the Canadian Arctic Archipelago (CAA) since 1998. The aim is to understand the variability in ocean and sea ice volume, heat and freshwater fluxes passing through the CAA and to determine their relationship to the ocean and ice budgets of the Arctic Ocean itself and to the circulation and vertical ventilation of the North Atlantic Ocean. Eight years of mooring data have now been processed and analyzed. The volume, freshwater and heat fluxes exhibit large seasonal and interannual variabilities with small fluxes in the fall and early winter and large fluxes in the summer. The seasonal mean volume flux estimates range from a low of 0.0Sv in the fall of 1998 to a maximum of 1.3Sv in the summer of 2000 (1Sverdrup=1.0x10ms). It has an 8yr annual mean of 0.7Sv and varies interannually by ±0.3Sv. Model simulations indicate that fluxes through Lancaster Sound make up 40-50% of the fluxes through the entire Canadian Arctic Archipelago, and that they are dependent on the sea level difference between the Beaufort Sea and Baffin Bay and on the horizontal density gradients across the CAA, observations of which are scarce or non-existent. Regression analysis with the Arctic Ocean wind field shows that the fluxes through the NW Passage measured in Lancaster Sound are significantly correlated with the far field wind forcing in the Beaufort Sea. The northeastward winds in the Beaufort Sea, parallel to the western side of the Canadian Arctic Archipelago, show the highest correlation on monthly to interannual time scales. This result is consistent with the transport being driven by a sea level difference between opposite ends of the NW Passage, and the difference being determined by setup caused by alongshore winds in the Beaufort Sea.