Thursday 25 August 2005

PBA1

PTH0158
Seasonal evolution of the upper thermal layer in the southern ocean south of Africa
Swart, Sebastiaan¹, Ansorge, Isabelle¹, Speich, Sabrina², Lutjeharms, Johann¹, Legeais, Jean-Francois²
1 Department Of Oceanography, University of Cape Town, South Africa
2 Laboratoire de Physique des Oceans, CNS/IFREMER/UBO, Brest, France
Author email: sswart@ocean.uct.ac.za
The Southern Ocean plays a critical role in the global oceanic thermohaline circulation, providing a vital link in the global transport of mass and heat. The ACC is by far the largest conduit by which, water, heat and salt are transferred between the Pacific, Atlantic, and Indian Oceans. The ACC carries approximately 134±13 Sv of polar and subpolar water masses from west to east through the Drake Passage. This interbasin exchange is an important link in the global overturning circulation and also allows anomalies such as eddies and rings formed in one basin to be carried around the globe, influencing climate in locations remote to the source. As these exchanges play an important role in regulating global climate, sustained hydrographic observations are essential in order to describe and understand better the physical and dynamic processes responsible for the variability of the ACC. Such intense and periodic monitoring has been underway in the Drake Passage and south of Tasmania since the 1970s. A repeat transect between South Africa and Antarctica, the third Southern Ocean 'choke point', was implemented in 2004. These repeat hydrographic measurements will be used to define suitable proxies between the thermal and dynamic height data, thus allowing the behaviour of the ACC, in particular its seasonality and inter-annual variability south of South Africa, to be studied in detail.

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