A synoptic description of the flow at Drake Passage from year‐long measurements

Abstract

The fronts and water mass zones comprising the Antarctic Circumpolar Current at Drake Passage have associated with them characteristic temperature structures. This property is used to construct maps that depict changes in the location of the fronts at 500 m. The zonation maps are based on temperature and velocity data obtained from 15 moorings deployed in the northern and central Drake Passage as part of the International Southern Ocean Studies experiment DRAKE 79. They provide a description of the flow of the Antarctic Circumpolar Current through Drake Passage at weekly intervals for a period of 1 year: January 1979 to January 1980. Mesoscale activity in central Drake Passage was dominated by the migration of three cold‐core rings and one warm‐core ring. The cold‐core rings formed from northward extending meanders of the Polar Front; the warm‐core ring from a southward extending meander of the Subantarctic Front. All four rings appeared to form within Drake Passage and to follow similar trajectories, which were influenced by local bathymetry. Variations in the location of the Subantarctic and Polar fronts were caused by meanders. In the narrowest portion of Drake Passage, when rings are present in the Polar Frontal Zone, the Polar Front is found farther south than when rings are absent.