A view of the Canary Basin thermocline circulation in winter

During January and February 1989 the recirculation of the subtropical gyre in the eastern North Atlantic was surveyed with a three-ship experiment. The analysis of hydrographic measurements and velocity data from a shipboard acoustic Doppler current profiler reveals the synoptic-scale circulation patterns and water mass distributions in the Canary Basin. The geostrophic transport stream function estimated with a horizontally varying reference level of no motion highlights the major currents in three layers representing the vertical structure of the horizontal circulation. The classical circulation scheme is shown by the stream function in the upper 200 m: the Azores, Canary, and North Equatorial currents. Unlike the deep-penetrating Azores Current, the Canary Current and the North Equatorial Current are restricted to the upper 200 m. Both carry North Atlantic Central Water along the water mass boundary with South Atlantic Central Water. South Atlantic Central Water flows through the passage between the Cape Verde archipelago and Africa via narrow currents into the area north of 14.5°N. At the southern edge of the subtropical gyre we identify an eastward flow of Antarctic Intermediate Water between 700 and 1200 m