The oceanic response to mesoscale atmospheric forcing

The response of the oceanic circulation to mesoscale atmospheric forcing is studied by comparing integrations of a global sea ice-ocean model with high-resolution European Centre for Medium-Range Weather Forecasts analysis data (0.4 degrees) to those with the same forcing coarse grained to a resolution typically employed in climate models and atmospheric reanalyses (1.8 degrees). It is shown that the representation of mesoscale features in atmospheric forcing fields leads to an increase in the strength of the wind-driven gyres in the North Atlantic and North Pacific regions of about 5-10% of its mean value. An increase of similar magnitude is found for the Atlantic meridional overturning circulation. From the results of this study it is argued that small-scale atmospheric phenomena such as fronts, mesoscale cyclones, and topographic jets play an important role in driving the mean oceanic circulation.