Starting in 2002 and as part of the NOAA Global Ocean Observing System, a new expendable bathythermograph (XBT) high-density line was started in the South Atlantic between Cape Town, South Africa and Buenos Aires, Argentina. (AX18 High-density XBT Line). The line was conceived to monitor the upper layer mass budget in the South Atlantic and to estimate the variability of the upper limb of the MOC transport. This page discusses quarterly estimates of meridional oceanic heat transport in the center of the South Atlantic Ocean subtropical gyre obtained from the data collected along this high-density line (AX18).