Marginal Sea Overflows for Climate Simulations

Abstract

This note describes a very simple parameterization of water mass transformation by marginal seas. This parameterization attempts to collapse marginal sea processes in to a sidew all boundary condition suitable for an OGCM. Exchange dynamics are treated by hydraulic control models and descent and mixing are treated by a model of a rotating entraining density current. This parameterization has been tested by comparison to some well measured overflows and it has been implemented in a z-level OGCM to see what effects marginal sea processes have on the deep circulation of an Atlantic-sized basin. Compared to an OGCM solution without a marginal sea but one which still has a vigorous thermohaline circulation the combined model solution has much better deep water properties and a rather different circulation in the northern basin.