Accelerated eddy shedding

Image of the Month - October 2012

Eddy Kinetic Energy trends per decade computed over the period 1993-2009. The Agulhas ring shedding seems to be accelerating. (Credits Nansen-Tutu Centre for Marine Environmental Research and University of Cape Town)

The Agulhas Current is one  of the most important currents, in particular due to the flux of warm and salty water from the Indian to the Atlantic Ocean its retroflection South of Africa generates -- typically in the form of Agulhas rings (eddies). This flow is now recognized as a key element in global climate, and changes in its flow linked to the glaciation/deglaciation has been shown.

Using satellite altimetry from 1993 to 2009, a study shows that the mesoscale variability of the Agulhas system, in particular in the Mozambique Channel and south of Madagascar, has intensified. The eddies shed have accelerated, which could be a mechanism compensating a deceleration of meridional overturning circulation associated with a freshening of the North Atlantic Ocean.

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References

  • B.C. Backeberg, P. Penven, M. Rouault, 2012. Impact of intensified Indian Ocean winds on mesoscale variability in the Agulhas system, Nature Climate Change, 2, 608–612, doi:10.1038/nclimate1587