On Thermally Forced Deep Equatorial Circulation in a GCM

Abstract

The thermohaline spinup of an equatorial ocean primitive equation GCM is investigated with a series of high-resolution numerical experiments. The author finds that a general problem of this class of models is unrealistically weak deep stratification combined with an unphysical parameterization of diffusion using vertical and horizontal coefficients. Near the equator, this leads to a heat balance between vertical advection and meridional diffusion. This balance, in turn, permits alternating zonal jets on the equator. The jets disappear when the deep stratification is improved to the extent that horizontal diffusion no longer dominates vertical diffusion. Therefore, the deep jet structures found in this and earlier studies are artifacts that are not related to observed equatorial deep jets.