COOLING OF THE WEST SPITSBERGEN CURRENT - WINTERTIME OBSERVATIONS WEST OF SVALBARD

The West Spitsbergen Current (WSC) is the major source of heat and sal t for the Arctic Ocean and the areas of deep convection in the Greenla nd Sea, The WSC current cools dramatically downstream. Hydrographic an d velocity data from a 3-week, midwinter cruise off Spitsbergen are us ed to investigate the heat budget of the WSC and the mechanisms of coo ling. The downstream divergence of mean heat flux in the WSC produces a heat loss of at least 1000 +/- 400 W m(-2) averaged over the width o f the Current, Approximately 350 W m(-2) is lost to the atmosphere and 200 W m(-2) is lost to melting ice over a region somewhat wider than the current. Cooling of the WSC to the atmosphere converts the inflowi ng Atlantic Water (AW) to Lower Arctic Intermediate Water, which is su fficiently salty to convect. Cooling by ice converts the AW to much fr esher Arctic Surface Water, which is too light to convect. The relativ e importance of these two conversions is primarily controlled by the F ate at which the wind advects ice from the Barents Sea over the WSC. T he warmest water of the WSC is often observed 100-200 m below the surf ace. Despite the lack of direct contact with the surface, this warm co re cools at about 800 W m(-2) in our observations. This rate is too la rge to be caused by diapycnal diffusion. We suggest that the energetic eddy held in this area diffuses heat along the steeply sloping isopyc nal surfaces that connect the warm core to the surface, renewing the s urface layer several times per day. This is consistent with the very s hallow surface mixed layers and high level of intrusions observed. We conclude that the surface layer of the WSC is cooled by the atmosphere and by ice from the Barents Sea and that isopycnal diffusion by mesos cale eddies continually renews this surface, thus cooling the interior bf the WSC. The relative magnitude of these processes determines whet her the inflowing warm, salty AW is converted to light, fresh surface water or salty, cold intermediate water.