Variability
of Antarctic Bottom Water Flow into the North Atlantic
Richard Limeburner, J. A. Whitehead and Claudia
Cenedese
Woods Hole Oceanographic Institution, Woods Hole,
MA 02543
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 1º S and 4º N with complex sidewall shape. At the
southern end is a 300 km wide zonal channel straddling the equator
between 32º W and 38º 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 (Hall et al., 1997) 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 is about the same as earlier at revisited
locations. The long-term drift of the deep Antarctic Bottom Water
temperature is of the order of -0.002º C/yr. Yearly averaged
velocities are about the same size as before at revisited locations,
and long-term trends of about the same size as before. The greatest
long-term temperature trend is found near the top of the deep Antarctic
Bottom Water at the northern edge of the current, as was evident in the
older data, too. 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.