Equatorial currents at 1000 m in the Atlantic Ocean

Twenty-seven Profiling ALACE (PALACE) floats were deployed in the equatorial Atlantic during July-August 1997. The floats were ballasted to drift at 1000 m for 10 to 14 days, return to the surface while obtaining a temperature profile, transmit data via satellite, and then after one day return to 1000 m. One-year float paths are now available. Floats deployed on the equator were launched into a deep westward jet. The jet extends some 1 degrees-2 degrees north of the equator, with eastward motion observed in floats to the north of 2 degrees N. The equatorial current reverses in the central basin to the east in mid-October and then back to the west in mid-February. Flow to the north also reverses. The short space and time scales contrast with earlier work based on fewer floats that inferred space scales of some 5 degrees-10 degrees in latitude and time scales greater than one year. The new results are consistent with models that indicate that equatorial Rossby waves are the cause of the reversing currents.