Interannual variations in the Atlantic meridional overturning circulation and its relationship with the net northward heat transport in the South Atlantic

摘要

Variability of the Atlantic Meridional OverturningCirculation (AMOC) and its effect on the net northwardheat transport (NHT) in the South Atlantic are examinedusing a trans-basin expendable bathythermograph (XBT)high-density line at 35°S (AX18). The time-mean AMOC is17.9 ± 2.2 Sv during 2002-2007. Although the geostrophictransport dominates the time-mean AMOC, both geostrophicand Ekman transports are important in explaining the AMOCvariability. The contributions of geostrophic and Ekmantransports to the AMOC show annual cycles, but they are outof phase, resulting in weak seasonal variability of the AMOC.The NHT variability is significantly correlated with theAMOC, where a 1 Sv increase in the AMOC would yield a0.05 ± 0.01 PW increase in the NHT. Partition of transportinto the western and eastern boundaries and interior suggeststhat, to quantify changes in the AMOC and NHT, it is criticalto monitor all three regions.