The southern Indian Ocean currents influence the south Atlantic Ocean

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15 July 2010

The Indian southern equatorial warmer current affects the biodiversity and the thermo-haline circulation of the Atlantic Ocean.

At Tara’s present location, the Agulhas current flows at high speed along Africa’s east coast (up to 6 knots). Arriving at the Cape of Good Hope (formerly called the Cape of Storms), this current meets up with the colder and polar currents from the Atlantic.  This results in a retroflection phenomenon where the Agulhas current turns on itself and proceeds eastward in the Indian Ocean.

During this retroflection, the Agulhas current creates meanderings, which evolve into rapidly turning eddies. Periodically some eddies detach from the current and traverse the Atlantic Ocean towards the American continent.

Each year, the dynamics of the eddies, which succeed each other in the Mozambique Channel, partially control food supply and marine predator displacement. Due to temperature and salinity conditions, in addition to diverse species trapped in their midst, these eddy masses influence the circulation and marine biodiversity of the south Atlantic.

One of the Tara Oceans’ goals is to precisely evaluate the role of these oceanic masses in their enrichment of the flora and fauna of the south Atlantic.

By sampling nascent eddies in the South Indian Ocean, and then following their peregrination in the Atlantic Ocean, the scientists will be fathoming the details of genetic dissemination on large oceanic scales.

As the last-born ocean, the Atlantic continues to benefit from the contribution made by its “big brothers” the Indian and Pacific, where the continuing regulation of oceanic exchanges creates an evolving situation, which remains to be studied.

Gaby GORSKY and Valérian MORZADEC