Global surface wave drift climate from ERA-40: the contributions from wind-sea and swell

By using 45 years of reanalysis data from the European Centre for Medium-Range Weather Forecasts, ERA-40, we present and discuss the global climatological wave-induced velocity, surface Stokes drift (SD), and its vertically integrated transport for deep water waves. We find that in most of the oceanic basins, the global surface SD is mainly wind-sea-driven while its vertically integrated transport is mainly swell-driven. The total surface SD does not always coincide in orientation with its vertically integrated transport. We suggest that such regions of misalignment are linked to “wave-driven wind” regimes. Coastal wave-induced transport divergences are mostly linked to wind-sea while divergences in the interior of the oceans basins are linked to swell. Analysis of trends indicates that the vertically integrated transport has generally increased during the 45 years analyzed. The largest increases are due to wind-sea in limited high-latitude areas while the swell has a minor increase, but over larger areas.