Prediction of mid-oceanic frontal passage confirmed in near-surface current measurements

Abstract

During May 1967, R. V. Chain systematically examined a mid-ocean thermal front in the region between 29°N and 31°N and 68°W and 71°W. A prediction was made aboard ship, based on the theory of Rossby waves, of the change in current direction and of the time this frontal zone would pass through 30°N, 70°W, where a current meter at 10 meters below the sea surface was moored. The current-meter record revealed a jet-like structure on June 6, 1967, as predicted, with a central strong current to the southeast corresponding to the frontal passage. Also, the jet-like current variations that occurred 25–40 days earlier on the record are likely to be associated with another portion of the same meandering westward-moving Rossby wave. This Rossby-wave interpretation of the thermal front and the success of the prediction of the current changes at a buoy 10 meters below the sea surface are complicated by the effects of the wind. Nevertheless, the mean flow directions exhibited in the two-month-long current record do not appear related to the winds.