Water Mass Transformation and Downwelling around Islands

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

Islands are dynamically interesting because they pose strong dynamical constraints on the exchange between the island shelf and the open ocean, and can result in important water mass transformation and export. These dynamics also influence the circulation on the shelf, on the slope, and far from the island. Idealized and realistic numerical ocean models will be combined with simple analytic models to better understand what controls water mass transformation and net downwelling around islands. The idealized framework emphasized here will provide a clearer understanding of why these processes differ between different islands and how they might be expected to change in a changing climate. Work supported by this grant will contribute to both undergraduate and graduate education programs at the Woods Hole Oceanographic Institution. The combination of analytic models and eddy resolving numerical models will provide insights into the dynamics and thermodynamics that control the diapycnal mass flux and mixing on island shelves and export of product waters to the surrounding ocean. Particular focus will be given to asymmetrical forcing situations in which the buoyancy-forcing, wind stress, surrounding ocean, or bottom topography vary around the island perimeter. The general approach will use theory to identify the relevant non-dimensional numbers and provide a dynamical framework with which to guide and interpret the numerical model calculations. The numerical models will be used to test the basic predictions from the theory while more completely resolving important processes such as nonlinear eddy fluxes and convection. Quantities of interest include: properties of product water masses; distribution of upwelling and downwelling; net diapycnal mass flux; induced circulations and fluxes across the shelf break.