Summary of Abstract Submission

Abstract Submission No. IO50-04-0003PresentationPoster

ANALYSIS OF COASTAL UPWELLING AT THE NORTH OF GULF OF GUINEA FROM OPERATIONAL MODEL AND OBSERVATIONS.

Bernard BOURLES*1

1 Research Director at IRD/CRHOB/ LEGOS, physical oceanography., France

ABSTRACT :

Sea surface temperatures (SSTs) and winds in the eastern tropical Atlantic are crucial for climate variability within the tropical belt. Despite this importance, state-of-the-art climate models show a large SST warm bias in this region. Temperatures in situ data have been collected during the Regional Physical Oceanography Program in West Africa (PROPAO) and were correlated with T321 Model ORCA 12 simulation data (provided by Mercator - Ocean). Statistics describing the onset of Coastal Upwelling (CU) index and the mean surface area shows that, most coastal upwelling along the Gulf of Guinea begins, the sooner it lasts and its area is great. Analysis of the heat content of the 20℃ isotherm and wind show that, the coastal upwelling Sassandra is strongly explained by the curl of the wind and those of Cotonou and Takoradi by the zonal wind stress. Zonal wind anomalies in the western equatorial Atlantic during late boreal winter to early summer precondition boreal summer cold/warm events in the eastern equatorial Atlantic (EEA) that manifest in a strong interannual Atlantic cold tongue (ACT) variability. The seasonal cooling essentially depends on the relative intensity of the local intraseasonal wind fluctuations; possibly linked to the St. Helena anticyclone, contribute to the variability of cold tongue and coastal upwelling onset and strength, particularly during years with preconditioned shallow thermoclines.