Cross-Isobath Transport of Shelf/Slope Water Driven by Offshore Eddies

At continental margins, energetic deep ocean eddies transport shelf water offshore in filaments that wrap around the eddy. A prominent example is that of Gulf Stream warm core rings interacting with the Mid Atlantic Bight shelf. The rate at which water is exported in these filaments is a major unknown in regional budgets of volume, heat and salt.

To help constrain this unknown transport, a series of idealized, primitive equation numerical experiments are conducted wherein a surface-intensified anticyclonic eddy interacts with idealized shelf-slope topography. There is no shelfbreak front in these experiments, and shelf water is tracked using a passive tracer. Most runs are conducted with a flat shelf; however, there is surprisingly little influence of the shelf's slope on transport magnitude. The model runs are used to construct an approximate model for the filament of exported water that originates inshore of any given isobath. This model is then used to derive an expression for the total volume of water transported by the eddy across that isobath. The transport scales with water depth, velocity scale of the eddy and length scale of the eddy. The resulting expression can be used in conjunction with satellite derived eddy properties and hydrographic data to estimate approximate real world transports in the absence of a shelfbreak front.