Drifter trajectories through a current meter array at Drake Passage

Six low‐profile undrogued buoys drifted through the Drake Passage during 1979 where an extensive array of current meters was moored. Geostrophic currents at the buoy positions are estimated by extrapolating the shallow 40‐hour low‐pass filtered current measurements to the surface by using vertical shear relationships derived from hydrographie stations taken over a 5‐year period within the passage. The buoy tracks are also filtered, followed by the removal of the extrapolated geostrophic currents. The residual drifts are then compared with the 10‐m winds, which are estimated twice daily by applying the similarity theory for a neutral barotropic boundary layer to sea level atmospheric pressure fields. The residual drifts are found to respond within a few hours to variations in the wind. Buoy motions against the interior flow, persisting for as long as 6 days, along with loops and reversals which are not observed in the subsurface currents are well accounted for by the wind. During times of nearly steady wind conditions the residual drift is found to average 3.4%±1.4% of the 10‐m wind speed at 25.0°±12.0° to the left of the wind.