Are ocean gyres driven by wind stress, surface buoyancy fluxes, or both?

Abstract

The large-scale ocean circulation is fuelled by a combination of winds and buoyancy (or heat) fluxes acting on the ocean’s surface. Gyres are central features of large-scale ocean circulation and are involved in the transport of many tracers like heat, nutrients, carbon-dioxide and so on within and across ocean basins. Traditionally, the gyre circulation is explained by the relationship between meridional transport and wind stress curl, known as the Sverdrup balance. However, it has been proposed that surface buoyancy fluxes may also contribute to the formation of gyres, although such a theoretical relationship is lacking in oceanographic literature. Through a series of eddy-permitting global ocean model simulations, we aspire to better understand the relative contribution of wind stress and surface buoyancy fluxes on large-scale ocean circulation. We perturb the atmospheric forcing by spatially varying the wind stresses and/or surface buoyancy fluxes, while minimising the associated changes in mixed layer dynamics. We compare perturbed forcing simulations with a control simulation in an attempt to decompose the large- scale ocean circulation into buoyancy and wind-driven components.