Cyclonic eddies formed at the Tropical Instability Wave fronts

Sea surface temperature images and surface drifter observations are compared to the results from a high resolution numerical simulation to study the properties of cyclonic eddies generated at the density front of the tropical instability waves in the Pacific. These cyclonic eddies, of which the diameter is about 50-150km and the vertical extent is limited to the upper 100 m in depth, have physical characteristics similar to those of smaller submesoscale eddies at the mid latitudes according to the model. They have highly coherent structures below the surface, carrying cold and salty upwelled equatorial water probably rich in marine life. The stretching and tilting of the upper layer of the ocean provides the main mechanism responsible for the intense cyclonic vorticity of the eddies, involving complex evolution of the density field into occluded fronts.