Hydrodynamics between Africa and Antarctica during Austral Summer of 2008 and 2009: Results of the IPY Project

A hydrographic section between Cape Town, South Africa and India Bay, Antarctica was sampled by deploying expendable CTD probes during the austral summer of 2008 and 2009. In 2009, the Agulhas Retroflection (AR) Front was displaced southward by 1.5 ̊ latitude, while the northern and southern Polar Front meandered southward by 1 ̊ and 1.4 ̊ latitude, respectively, relative to their positions in 2008. Geostrophic transport, relative to 1000 m, indicates that Antarctic Circumpolar Current (ACC) flow decreased by 2.5 Sv in 2009 compared to that in 2008. The anticyclones which are detached from the AR facilitates a transport to the southeast Atlantic Ocean ranging between 8 and 12 Sv. Nearly 50% of the ACC transport is confined to the 100 500 m layer. A comparison of water mass distribution for 2008 and 2009 suggests that Mode Water distribution was restricted to 42.5 ̊S and 41.9 ̊S, and the Antarctic Surface Water extended to 57.6 ̊S and 46.6 ̊S, respectively. In 2009, the along track Heat Content (HC) and Salt Content (SC) for the upper 750 m of the water column decreased each by 1% compared to those in 2008. In the ACC domain, the HC and SC dip by 36% and 40% in 2009, respectively. The HC and SC associated with Agulhas Retroflection Front increase in 2009 by 1% and 2%, respectively, due to an enhanced Agulhas transport of warm and saline water from the tropics by 2%.