The Agulhas current leaks

Image of the Month - August 2014

(a) Mean values of absolute dynamic topography (contours) and its standard deviation (color, in cm2) with the Topex/Poseidon satellite tracks used for this work. (b) Anomalies with respect to the time average of the Agulhas leakage volume transport computed from satellite altimetry along three satellite tracks. (Credits Utrecht University)

Waters from the Indian Ocean, carried by the Agulhas Current separate from it when it turns sharply back East, becoming the Agulhas Return Current. The volume of the water exchanges between Indian and Atlantic Ocean is linked to this "leakage" of relatively warm and salty water separating from the Agulhas Current. However, discriminating between the different flows of currents South of Africa is quite difficult, especially when you want only the waters from the Indian Ocean to be taken into account. A new study proposes to measure the "leakage" indirectly by looking at the difference in volume transport between the Agulhas Current and its return current. Several T/P-Jason-1-Jason-2 tracks cross at right angle both the Agulhas Current and its Return. These can be used to estimate the difference between both flows.

Using this technique, and twenty years of altimetry data, the evolution of the Agulhas leakage, and thus of the water exchanges between Indian and Atlantic Ocean has been computed. Studying the impact of their variability on the climate is the next step.

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