Deep jets in the equatorial Atlantic Ocean

Deep velocity profiles taken in the equatorial Atlantic Ocean show equatorially trapped deep jets with similar features to those of the Indian and Pacific Oceans: a zonal velocity of the order of 10 to 20 cm s(-1) and a meridional scale of 1 degrees. In the Pacific and Indian Oceans the zonal extent of the jets is at least 150 of longitude. Owing to the lack of synoptic measurements, we have no information on the zonal scale in the Atlantic Ocean, but we present here zonal velocity profiles, made at a 16-month interval, that have identical baroclinic structure in the western (35 degrees W) and central basin (13 degrees W). The Atlantic jets have a vertical scale larger (400-600 m) than those observed in the Pacific Ocean (250-400 m). Our measurements confirm the opposite directions of the jets for different seasons in the Atlantic Ocean. Furthermore, for a given season, the vertical profiles of zonal velocity at 35 degrees W-0 degrees are astonishingly similar at a 5-year interval. As in the Pacific and Indian Oceans, the jets are embedded in a large-vertical-scale current that changes direction with time. The few profiles available in the equatorial Atlantic Ocean suggest a seasonal reversal of the jets, but neither this nor the temporal variability of the large-scale current has been adequately resolved.