Large-Scale Dynamics of Circulations with Open-Ocean Convection

Abstract

AbstractFormation of the densest water masses in the North Atlantic and its marginal seas involves open-ocean convection. The main goal of this study is to contribute to the general understanding of how such convective regions connect to the large-scale ocean circulation. Specifically, analytic and numerical versions of a variable density layer model are used to explore the processes underlying the circulation in an idealized ocean basin. The models are forced by a surface buoyancy flux, which generates a density maximum in the ocean interior. In response to the forcing, a region forms that is characterized by the closed Rossby wave characteristics and where the eddy–mean transport converges toward the convective site. Outside of that region, characteristics extend from the eastern boundary and a distorted β-plume circulation develops, linking the convection site with the western boundary. The overturning strength in the model can be related to several environment variables and forcings and is constrained by the surface density field, stratification, eddy mixing strength and by Rossby wave dynamics. Solutions forced by an interior ocean density minimum are also considered. Although no convection occurs, the dynamics underlying the circulation are closely related to the case with cooling.