Speaker
Description
The South Atlantic Meridional Overturning Circulation (SAMOC) observing system has evolved tremendously since 2007, and has substantially improved our understanding of the dynamics and variability of the upper, deep, and abyssal South Atlantic circulation from daily to interannual time-scales. However, the SAMOC daily time series derived from moored arrays are still relatively short and are only available at 11°S and 34.5°S. To expand the SAMOC time series in space and time, we derived monthly zonal trans-basin temperature (T) and salinity (S) sections since 1993 at four latitudes (20°S, 25°S, 30°S, and 34.5°S) based on historical relationships between T, S, and satellite sea level. The resulting meridional overturning circulation (MOC) and meridional heat transport (MHT) estimates at 20°S, 25°S, and 30°S are significantly correlated with each other at near zero lag, however correlations with the estimates at 34.5°S are somewhat lower. Although the overturning contribution dominates changes in the MHT at all four latitudes, the gyre contribution increases southward, reaching 30% of the explained MHT variability at 34.5°S. These 30-year monthly records indicate that the dominant mechanism controlling the MOC/MHT variability alternates between wind forcing and internal ocean dynamics. Therefore, both mechanisms must be monitored to fully capture changes in the MOC/MHT. These estimates demonstrate a linkage between the tropical Pacific forcing and heat content changes in the subtropical South Atlantic, as well as the impact of the MOC/MHT on extreme weather events, and provide context for measurements obtained from the SAMOC moored arrays.
