The formation of polar surface water, the ice export and the exchanges through the Fram Strait

Abstract

The Polar Surface Water is formed from two parent water masses: inflowing Atlantic water and fresh from river run-off and net precipitation. Two possible modes for this formation are considered: 1. (a) Entrainment, driven by mechanical stirring, takes place over the entire Polar Ocean and brings Atlantic Water into the surface layer. 2. (b) The interaction between the Atlantic Water and the fresh water supply occurs only on the s shelves, while the mixing in the interior is inhibited by a thick advective layer of intermediate density formed on the shelves. The exchanges between the Polar Ocean and the North Atlantic and the resulting stratification are determined for the two cases. The derived transports are much smaller than those often encountered in the literature. Which mode dominates, depends upon the fresh water discharge. From the analysis it is found that a larger fresh water contribution favours mixing on the shelves, while the entrainment in the interior becomes more important as the run-off diminishes. The present day situation is probably one where the shelf processes dominate. However, a modest decrease in the river run-of the Ocean. It is found that a complete removal of the river run-off may not affect the extent of the ice cover too seriously so that comparatively high ice export can be maintained. This is because the higher salinity of the Polar Surface Water gradually increases the fresh water buffer present in the Pacific inflow.