Combining altimetry with a thermocline model to examine the transport of the North Atlantic

Abstract

The relationship between sea surface height and transport is explored using a steady, geostrophic, thermocline model. Given an imposed sea surface height (SSH), analytical solutions reveal different patterns for the transport over the interior of a subtropical gyre determined by the background stratification. For no mixed layer or the limit of weak stratification, transport increases more rapidly westward than SSH across a subtropical gyre, whereas in the limit of strong stratification, transport increases linearly with SSH, and streamlines become more orientated from the northwest to southeast. A modified version of the thermocline model is applied to the subtropical gyre of the North Atlantic and uses SSH from TOPEX/Poseidon altimetry and a functional relationship between potential vorticity and density derived from the National Oceanographic Data Center climatology. The model suggests that the transport over the interior of the subtropical gyre reaches 30±13 Sv, which is broadly in accord with the independent Sverdrup estimate from the wind‐stress climatology. The transport pattern includes a north‐south asymmetry, which is consistent with both the mixed layer and background stratification influencing the solution.