XBT (eXpendable BathyThermographs) transect AX18, which runs between Cape Town and South America (Montevideo, Uruguay, or Buenos Aires, Argentina) is geared towards improving the current climate observing system in the South Atlantic, a region of poor data coverage. The goal of AX18 is to monitor the meridional mass and heat transport in the upper 800 m across 30^oS. Given the importance of the South Atlantic and the scarcity of observations in this region, data obtained from the measurements along this transect will be used to investigate the role of the South Atlantic in improving climate forecasts.