A kinematic model of wind-driven meridional heat transport

Abstract

A kinematic model of flow in the subtropical gyre is used to estimate the upper-ocean temperature distribution and heat transport that is forced by the wind-driven circulation. The temperature is idealized as a passive tracer forced by a zonally constant Haney condition and advected by a barotropic gyre. The simplicity of the model allows for analytical solutions, which are in fairly good quantitative agreement with the results obtained by Wang et al. using a numerical model. In particular, the maximum heat transport Q occurs when the restoring timescale for temperature is about one-tenth of the time it takes a particle to flow around the gyre. Estimates for the actual heat transport carried by the subtropical gyre are 0.2-0.4 PW for the North Atlantic and 0.3-0.6 PW for the North Pacific. Finally, the model shows that when the restoring timescale is short compared to the gyre advection timescale, the heat transport is sensitive to the width of the western boundary current. Potentially this could lead coarse-resolution numerical models to underestimate meridional heat transport, but the actual restoring timescale of the ocean may be too long for this to be an important effect.