A Limited-Area Primitive Equation Model of the Gulf Stream: Results in Statistical Equilibrium

Abstract

Abstract An eddy-resolving circulation model has been applied to the Gulf Stream System from Cape Hatteras to east of the Grand Banks (78-45 W, 30-48 N). The primitive equation model has realistic coastlines, bottom topography, and forcing functions. A two-layer version was driven by observed mean climatological wind forcing and mass transport prescribed at inflow. Outflow was determined by a radiation boundary condition and an integral constraint on the mass field in each layer. Specification of a Deep Western Boundary Current (DWBC) was included in some model runs. Results from a sequence of experiments suggest an important role for the DWBC in determining the mean path of the Gulf Stream and consequently the distribution of eddy kinetic energy, and the character of the deep mean flow. The most realistic experiment compares to within a factor of two or better with observations of the amplitude of eddy kinetic energy and rms fluctuations of the thermocline and sea surface height. Abyssal eddy kinetic energy was less than observed. The mean flow is characterized by recirculations to the north and south of the Gulf Stream and a deep cyclonic gyre just east of the northern portion of the New England Seamount Chain, as found in the data.