Diagnostic and prognostic numerical circulation studies of the South Atlantic Bight

TLDR

The study presents results from diagnostic and prognostic numerical simulations of circulation in the South Atlantic Bight. The authors employ a three‑dimensional, primitive‑equation σ‑coordinate model with turbulent closure, implicit vertical scheme, and mode‑splitting, and they specify realistic initial conditions, surface forcing, and lateral open boundaries derived from a diagnostic geostrophic‑Ekman model. The simulations reproduce key features of the South Atlantic Bight circulation, including shallow shelf and Gulf Stream‑dominated deep waters, but synoptic skill assessment data are unavailable.

Abstract

Some of the results from a series of diagnostic and prognostic numerical simulations of the circulation in the South Atlantic Bight (SAB) are described. The numerical model developed for the study is a three‐dimensional, primitive equation, time dependent, σ coordinate model with an imbedded, turbulent closure submodel which should yield realistic Ekman surface and bottom layers. An implicit numerical scheme in the vertical direction and a mode‐splitting technique in time are adopted for computational efficiency. A significant portion of the paper is concerned with realistic specification of initial conditions for temperature and salinity, surface forcing, and lateral open boundary conditions. The latter are determined by a simple diagnostic (geostrophic and Ekman dynamics) model which provides dynamically consistent temperature, salinity, and velocity boundary conditions. It appears from an exaination of the numerical simulations that the full model yields results that share many features in common with our general understanding of the circulation of the South Atlantic Bight; the region includes shallow shelf waters as well as deeper water dominated by the Gulf Stream. Data for synoptic skill assessment, however, are not available.