Description: Over the past decade it has been demonstrated unequivocally that the exchange of water masses between the Indian and the Atlantic oceans, south of Africa, is a key component of the global thermohaline circulation cell. This thermohaline circulation plays a large part in controlling global climate. Numerous South African and international studies have now been completed on these water exchanges, but most have concentrated their efforts on the upper water masses. We descriptionbe here an extensive and exciting new venture, called KAPEX, to investigate the movement of water at intermediate depths using sophisticated Lagrangian floats. This research programme is a collaborative effort between research groups from three countries and constitutes the geographically largest oceanographic experiment ever carried out in South African waters. Detailed information on the aims as well as the progress of KAPEX is available on the Internet on the home page http://triton.sea.uct.ac.za

Description: The objective of this paper is to evaluate the baroclinic and barotropic components of sea surface height (SSH) anomalies in the Southern Ocean and investigates the causes for the weak correlation between hydrographically derived and satellite measured SSH anomalies. To this end, data obtained by six Pressure Inverted Echo Sounders (PIES) deployed south of Africa were used to derive baroclinic and barotropic SSH anomalies. Our results show that the barotropic component accounts for 30%–60% of the variability between the jets of the Antarctic Circumpolar Current (ACC). In contrast, the jets associated with the major ACC fronts are predominantly baroclinic. The deep baroclinic component is important in the ACC and accounts for the major part of the baroclinic variability. The comparison with along-track satellite altimetry (Jason 1/2) shows correlations coefficients of 0.24–0.92, with low values in regions of high-barotropic variability. The comparison with gridded Aviso satellite altimetry generally shows higher correlation coefficients (0.33–0.92) and lower root mean square (RMS) errors compared to the along-track product. In conclusion the barotropic SSH anomaly plays a major role in this region and has to be accounted for when assimilating SSH into ocean models. Due to their high-baroclinic component, the correct representation of the time and space varying ACC fronts seems to be crucial for the right SSH anomaly partitioning used for assimilation purposes. Gridded products, namely Aviso, seems to be more suitable compared to along-track products (Jason 1/2) in representing the variability of SSH anomalies.