Relative vs. absolute wind stress in a circumpolar model of the Southern Ocean
David Munday, Xiaoming Zhai, James Harle, Andrew C. Coward, A. J. George Nurser
Abstract
The transfer of momentum between the atmosphere and ocean is dependent upon the velocity difference between the seawater and overlying air. This is commonly known as relative wind, or ocean current interaction, and its direct effect is to damp mesoscale ocean eddies through the imposition of an opposing surface torque. If an ocean model neglects the ocean velocity in its bulk formulae, this can lead to an increase in power input to the ocean and a large increase in Eddy Kinetic Energy (EKE). Other secondary effects that are dependent upon the current system under consideration may also occur. Here we show that the neglect of relative wind leads to an ∼50% increase in surface EKE in a circumpolar model of the Southern Ocean. This acts to increase the southwards eddy heat transport, fluxing more heat into the seasonal ice zone, and subsequently reducing ice cover in all seasons. The net reduction in planetary albedo may be a way for a largescale impact on climate.