Southern Ocean Response to Relative Velocity Wind Stress Forcing

An eddy resolving quasi-geostrophic model of the Southern Ocean coupled to a dynamic atmospheric mixed layer is used to compare the performance of two different wind stress parameterisation schemes. The first is the standard quadratic drag law based on atmospheric velocity alone, while the second (more exact) formulation is based on the difference between ocean and atmosphere velocities. The two different schemes give very similar magnitudes of mean stress, but the relative velocity scheme has substantially lower power input, resulting in a weaker eddy field and consequently greater circumpolar transport. These results are explored in terms of existing theories of the Antarctic Circumpolar Current (including eddy saturation and eddy damping) and the implications for modelling the Southern Ocean are discussed.