Observations of SST‐Induced Wind Perturbations in the Leeuwin Current

Abstract

AbstractSea surface temperature (SST) perturbations modify low‐level winds through the influence of air‐sea heat flux across the marine atmospheric boundary layer, mostly observable in the major western boundary current systems. In this study, we investigate the effects of SST on surface winds in a poleward‐flowing eastern boundary current system, the Leeuwin Current (LC), using the Advanced Very High‐Resolution Radiometer (AVHRR) SST and wind data from Cross‐Calibrated Multi‐Platform (CCMP) during 2009–2018. There exist robust linear relationships between perturbation SST and perturbation wind speed and their derivatives in the LC. The regression slopes between SST perturbations and wind perturbations appear to be higher in austral summer when the alongshore northward winds are strongly opposing the LC, however, the relationships in winter are statistically more robust when the LC and associated cross‐shore SST fronts are the strongest. Consistent with previous studies in the western boundary currents, crosswind perturbation wind speed gradient is the largest for the winds 80° (−100°) to the right (left) of the SST gradient in the LC region. The perturbation wind stress curl induced by the SST signature of the LC causes positive wind stress curl anomalies on the offshore edge of the LC, driving anomalous downwelling and would reduce surface chlorophyll a concentrations along the LC SST front as observed in satellite data, which may have implications in regional biogeochemistry.