Cooling of the West Spitzbergen Current: Wintertime Observations West of Svalbard.

摘要

The West Spitzbergen Current (WSC) is the major source of heat and salt for the Arctic Ocean and the areas of deep convection in the Greenland Sea. The WSC current cools dramatically downstream. Hydrographic and velocity data from a 3-week, midwinter cruise off Spitzbergen are used to investigate the heat budget of the WSC and the mechanisms of cooling. The downstream divergence of mean heat flux in the WSC produces a heat loss of at least 1000 + or - 400 Wm-2 averaged over the width of the current. Approximately 350 Wm-2 is lost to the atmosphere and 200 Wm-2 lost to melting ice over a region somewhat wider than the current. Cooling of the WSC to the atmosphere converts the inflowing Atlantic Water (AW) to Lower Arctic Intermediate Water, which is sufficiently salty to convect. Cooling by ice converts the AW to much fresher Arctic Surface Water, which is too light to convect. The relative importance of these two conversions is primarily controlled by the rate at which the wind advects ice from the Barents Sea over the WSC. The warmest water of the WSC is often observed 100-200 m below the surface. Despite the lack of direct contact with the surface, this core cools at about 800 Wm-2 in our observations.