The response of the southern annular mode, the east Australian current, and the southern mid-latitude ocean circulation to global warming

Abstract

Climate models predict an upward trend of the Southern Annular Mode (SAM) in response to increasing atmospheric CO2 concentration, however the consequential impact of this change on oceanic circulation has not been explored. Here we analyse the outputs of a series of global warming experiments from the CSIRO Mark 3 climate model. We show that although for the zonal wind stress change the maximum is located at approximately 60S, in terms of the change in surface wind stress curl, the maximum is situated at approximately 48S. This change in the wind stress curl causes a spin-up of the entire southern midlatitude ocean circulation including a southward strengthening of the subtropical gyres, particularly the East Australia Current (EAC). The intensified EAC generates a warming rate in the Tasman Sea that is the greatest in the Southern Hemisphere (SH) with significant implications for sea level rise. The pan-Southern Ocean scale suggests a broad impact on the marine ecosystem of the entire southern midlatitude ocean.