Deep waters of the Arctic Ocean: origins and circulation

Abstract

The Oden 91 Expedition has provided a data set that makes it possible to deduce more detailed ideas regarding the origin and circulation of waters in the Arctic Ocean. The three possible sources for the deep water of the Arctic Ocean are: (1) density flows down the continental slope triggered by brine enhanced waters formed on the continental shelves but consisting primarily of waters entrained from the Atlantic and intermediate layers; (2) inflow of Atlantic Water over the Barents Sea shelf that has experienced a density increase by cooling and freezing in that sea and then sinks with little entrainment down the St Anna Trough into deep layers of the Arctic Ocean; and (3) the inflow of Norwegian Sea Deep Water through Fram Strait. Of these three sources, the first appears to contribute the most to the Arctic Ocean deep water and the third the least. The Eurasian Basin communicates with the Canadian Basin through a boundary current that enters the Canadian Basin north of Siberia and leaves it north of Greenland. The fact that both the temperature and salinity are higher in the Canadian Basin than in the Eurasian Basin at levels above as well as below the sill depth of the Lomonosov Ridge indicates that slope convection is active in the Canadian Basin. The deepest layers have constant salinity, but show a weak temperature decrease towards the bottom. This suggests that these layers of the Canadian Basin are not primarily renewed by convection down the continental slope but by a spill over of Eurasian Basin Deep Water across the central part of the Lomonosov Ridge. A model which incorporates density flows triggered by high salinity shelf water and water overflowing the Lomonosov Ridge flom the Eurasian Basin is applied to reproduce the observed profiles of the Canadian Basin and to establish the relative importance of these two sources. By incorporation of I4C profiles into the model, estimates of the exchange rates of water in these layers can be made.