The surface thermal signature and air–sea coupling over the Agulhas rings propagating in the South Atlantic Ocean interior

[摘要] The surface signature of Agulhas rings propagating across the South AtlanticOcean is observed based on three independent data sets: Advanced Microwave Scanning Radiometer for the Earth Observing System/Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) (TMI/AMSR-E) satellite seasurface temperature, Argo profiling floats and a merged winds productderived from scatterometer observations and reanalysis results. A persistentpattern of cold (negative) sea surface temperature (SST) anomalies in the eddy core, with warm(positive) anomalies at the boundary, is revealed. This pattern contrastswith the classical idea of a warm core anticyclone. Taking advantage of amoving reference frame corresponding to the altimetry-detected Agulhasrings, modifications of the surface winds by the ocean-induced currents andSST gradients are evaluated using satellite SST and wind observations. Asobtained, the averaged stationary thermal expression and mean eddy-inducedcirculation are coupled to the marine atmospheric boundary layer, leading tosurface wind anomalies. Consequently, an average Ekman pumping associatedwith these mean surface wind variations consistently emerges. Thisaverage Ekman pumping is found to explain very well the SST anomalysignatures of the detected Agulhas rings. Particularly, this mechanism seemsto be the key factor determining that these anticyclonic eddies exhibitstationary imprints of cold SST anomalies near their core centers. Aresidual phase with the maximum sea surface height (SSH) anomaly and wind speed anomaly is foundto the right of the mean wind direction, apparently maintaining a coherentstationary thermal expression coupled to the marine atmospheric boundarylayer.

[学科分类] 海洋学与技术