Hydrography of the West Spitsbergen Current, Svalbard Branch: Autumn 2001

The Atlantic inflow is the primary source of water and heat to the Arctic Ocean. A large portion enters through Fram Strait where it splits into the Yermak and Svalbard Branches. In October to November 2001 the USCGC Healy occupied five oceanographic transects across the Svalbard Branch west and north of Spitsbergen. Temperature and salinity sections show the warm, salty Atlantic Water cooling and freshening as it flows along the continental slope for 553 km. The temperature in the upper 500 m of the water column decreased by 0.25 degrees C/(100 km) implying a heat flux across the sea surface of up to 520 W/m(2) if one assumes a nominal current of speed of 0.1 m/s. A temperature-salinity (T-S) analysis shows that the shape of the T-S curves can be explained in terms of the ratio of the atmospheric-to-ice-melt heat flux. The observations imply that ice melt accounts for progressively more surface cooling as the flow moves toward the Arctic Ocean. An autonomous underwater vehicle completed a vertical section in the region of maximum water mass gradient and revealed layer interleaving in fine detail. Data from this cruise extend a long time series of Atlantic layer source temperature beginning in 1910 (Saloranta and Haugan, 2001). The extended observations show that after the temperature of the Atlantic layer inflow reached a peak in 1992, it cooled to a minimum in 1998 and rose again through 2001.