CHLOROFLUOROMETHANE DISTRIBUTIONS IN THE DEEP EQUATORIAL ATLANTIC DURING JANUARY-MARCH 1993

Chlorofluoromethanes were sampled along two zonal sections, at 4 degre es 30 S and 7 degrees 30 N between the African and American continents (A7 and A6 WOCE sections) and two meridional sections, at 35 degrees W and 3 degrees 50W, during the CITHER 1 cruise (part of the French pr ogram CITHER (CIrculation THERmohaline) during January-March 1993. The results reported here deal primarily with the North Atlantic Deep Wat er, just ten years after the first CFM snapshot of the tropical Atlant ic ocean obtained during the Transient Tracers in the Ocean Program (T TO) (Weiss et al., 1985. Nature 314, 608-610). The data provide eviden ce for the eastward bifurcation of the deep flow near the equator, on both UNADW and LNADW levels. The distributions clearly show the CFM si gnal corresponding to the UNADW penetrating into the eastern basin: at 3 degrees 50W the CFM core extends from 4 degrees S to 3 degrees N wi th a maximum around 2 degrees S. On both UNADW and LNADW levels, the b ifurcation does not occur exactly on the equator but a few degrees sou th and seems to be partly induced by topographic effects. Previously p ublished circulation schemes for UNADW and LNADW levels are compared t o the CITHER 1 CFM data. Great variability is revealed and new pattern s from the data are highlighted. The ''young'' deep component of the A ABW flow seems to be stopped by the topography just north of the equat orial channel. TTO and CITHER 1 data set comparison and ''apparent'' a ges lead to minimal values of the propagation rate of the CFC signal a t low latitudes. (C) 1998 Elsevier Science Ltd. All rights reserved.