Numerical simulation of the Gulf Stream System: The Loop Current and the deep circulation

Abstract

The Loop Current and the deep circulation in the Gulf of Mexico are numerically investigated by a primitive equation, sigma coordinate ocean model with realistic surface fluxes obtained from an atmospheric forecast model. A deep cyclonic circulation, bounded by the deep basin in the eastern Gulf of Mexico, is spun up by the Loop Current; the deep cyclonic circulation is coincident with a southward current of the Loop Current eastern limb and weakens after Loop Current ring separation and cessation of the southward current. The anticyclonic, semienclosed Loop Current also induces anticyclonic lower layer columnar eddies in the eastern gulf. These lower layer eddies decouple from the upper layer Loop Current. The westward translation speed of a Loop Current ring is about 2.16-5.18 km d-1; the lower layer eddies have a higher speed and lead the rings into the central gulf. The time-averaged surface circulation of the Gulf of Mexico basin is anticyclonic, mainly because of the transport of anticyclonic vorticity by Loop Current rings in the surface layer an average lower layer cyclonic circulation occurs along the continental slope of the basin.