Interannual variability and regional impacts in the Tropical Atlantic Ocean
Bernard Bourles (LEGOS)
Contrary to the Pacific Ocean, where the dominant mode of variability, the El Niño-Southern Oscillation (ENSO), occurs on an interannual timescale, the dominant mode of variability in the tropical Atlantic Ocean occurs mainly on annual timescales. Moreover, the large scale variability of the Atlantic is much more complex than the Pacific one, both in time and space. It is usually split into an interannual variability, with equatorial warm events analogous to, but weaker than, the ENSO and into decadal timescale of variability, with sea-surface temperature (SST) varying almost in opposition north and south of the equator. Many mechanisms of the large scale variability of the tropical Atlantic are not well understood and are still under debate. For instance, is the ocean by itself playing a major role in the decadal variability? Is this variability limited to a few regions only or to the entire Atlantic basin? Remote forcings versus local forcings of this large scale variability also raise controversial theories about the ENSO influence, the North Atlantic Oscillation (NAO) or the southern Ocean forcings.
Altimetry, and more generally satellite missions, is interesting as it covers the global ocean. New missions such as the next coming SARAL/Altika altimetry mission, or the future SWOT mission, are some promising and challenging tools to approach coastal oceanography.
The aim of this OSTST proposal is thus to analyse the large scale variability of the tropical Atlantic, on an interannual basis, from the series of TOPEX/Poseidon, Jason1&2 data covering the 1993-2012 period, and to benefit from the new generation of altimetry missions to focus on the local impacts/variability over some key regions: the western coast, the Gulf of Guinea, and the Dakar and Benguela upwelling areas.