Modulation of the Ocean Surface Skin Temperature and Heat Flux in the Presence of Strong SST Fronts

Abstract Previous studies of air‐sea interactions over sharp oceanic fronts have suggested that it is the ocean that drives the atmosphere across sub‐mesoscale ocean fronts, but it is the atmosphere that drives the ocean at synoptic scales; the responsible mechanism, however, is still a matter of debate. This paper examines direct sea surface temperature ( SST ) measurements of the skin ( SST skin ) and near‐surface SST ( SST depth ), and wind speeds measured during the Sub‐Mesoscale Ocean Dynamics Experiment (S‐MODE) along with derived bulk fluxes. We evaluate the modulation of the net heat flux, wind speed, and skin cooling across SST fronts and the ability of the COARE bulk flux algorithm to reproduce this variability. Bulk flux computations can be performed directly from a radiometric SST skin , or more commonly, from the SST depth provided that the depth of the SST measurement is corrected for cool skin and diurnal warming effects. Both types of SST were measured during S‐MODE allowing for (a) an assessment of the importance of having a SST skin for a direct flux evaluation in frontal regions, and (b) an evaluation of the accuracy of the cool skin and diurnal warming corrections within COARE for the indirect bulk flux computation. The ocean‐atmosphere feedback over the sampled S‐MODE submesoscale front suggested that the ocean was indeed forcing the atmosphere, mainly through the surface net heat losses, while the wind response to changes in SST skin was irregular. Testing of the COARE algorithm suggested that indirect bulk fluxes had sufficient accuracy to close the heat budget over the front.