The Influence of Deep Mesoscale Eddies on Sea Surface Temperature in the North Atlantic Subtropical Convergence

Maps of sea surface temperature in the North Atlantic subtropical convergence during the 1973 MODE field experiment (and recent satellite imagery) show large meridional and zonal features on a scale of 40-400 km which are superimposed on the seasonal meridional temperature gradient. After comparing these maps with dynamic topography relative to 1500 db, it is argued that these features are mainly due to advective distortion by surface currents associated with the deep baroclinic mesoscale eddy field. Wind-induced surface currents appear to have a lesser effect in generating such structure. Surface frontogenesis observed during MODE and by earlier workers in the area suggests that jet-like shallow surface density currents may also be significant in advecting and distorting the surface temperature field on scales of 10 km and less. Rough calculations indicate that these advective processes of the sea surface may supply annually an amount of heat to the surface water mass of the northern Sargasso Sea which is significant compared with that lost to the atmosphere.