Variability of Antarctic bottom water flow into the North Atlantic

The flow of Antarctic bottom water from the Brazil Basin in the South Atlantic into the Guiana Basin in the western North Atlantic has been measured by current meters for 44 months. Flow is confined by a relatively flat 4500-m-deep passage between 1° S and 4° N with complex sidewall shape. At the southern end is a 300-km-wide zonal channel straddling the equator between 32° W and 38° W with approximately a 500-m-deep layer of bottom water. The deep Antarctic bottom water current into the North Atlantic is confined to a region south of the equator and the direction is westward. Previous measurements of this deep current over 600 days in duration (J. Phys. Oceanogr. 27 (1997) 1903) indicated both a small warming trend and a decreasing volume flux. New data presented in this paper of 1388 days duration show no evidence for continuation of such trends. The average temperature and yearly averaged velocities are about the same as earlier at revisited locations. The long-term drift of the deep Antarctic bottom water temperature is about -0.002 ° C/year and drift of the westward velocity is about 0.0015 m/s/year. The greatest variability is found near the top of the deep Antarctic bottom water at the northern edge of the current. The spectrum of the new 44-month data reveals a distinct yearly peak. We conclude that there has been no change in Antarctic bottom water flux into the North Atlantic during the past decade. © 2005 Elsevier Ltd. All rights reserved.