Physical oceanography studies in the Weddell Sea during the Norwegian Antarctic Research Expedition 1978/79

Abstract

Hydrographic and current measurements obtained during the Norwegian Antarctic Research Expedition 1978/79 to the southern Weddell Sea are presented. Cold, dense Ice Shelf Water circulating under the floating ice shelves is observed to leave the shelf as a concentrated bottom flow. From moored current metres this discharge is estimated at 0.7. lo6 m3/s at -2.o"C (one year average) and with no appreciable seasonal variation. This contribution to the Weddell Sea Bottom Water is clearly identified through extreme temperature gradients at our deepest stations (below 2500 m). The core of Weddell Deep Water shows a considerable (T ~ 0.5"C) warming up since 1977, presumably due to the lack of polynya activity in the intervening period. Measurements in the coastal current at the ice shelf (70%. 2"W) show step structures which are probably due to cooling and melting at the vertical ice barrier. Slight supercooling due to circulation under the ice shelf is also seen. The net effect of the ice shelf boundary seems to be a deep reaching cooling and freshening of the coastal current providing the low salinity. freezing point Eastern Shelf Water. This process is considered a preconditioning which enhances production of the saline Western Shelf Water which in turn is transformed to Ice Shelf Water.