Satellite observations of the small-scale cyclonic eddies in the western South China Sea

[摘要] High-resolution ocean color observations offer an opportunity to investigatethe oceanic small-scale processes. In this study, the Medium ResolutionImaging Spectrometer (MERIS) daily 300 m data were used to study small-scaleprocesses in the western South China Sea. It is indicated that the cycloniceddies with horizontal scales of 10 km are frequently observed during theupwelling season of each year over the2004–2009 period. These small-scale eddies weregenerated in the vicinity of the southern front of the cold tongue, and thenpropagated eastward with a speed of approximately 12 cm s⁻¹. Thispropagation speed was consistent with the velocity of the western boundarycurrent. As a result, the small-scale eddies kept the high levels ofphytoplankton rotatingaway from the coastal areas, resulting in the accumulation ofphytoplankton in the interior of the eddies. The generation of thesmall-scale eddies may be associated with strengthening of the relativemovement between the rotation speed of the anticyclonic mesoscale eddies andthe offshore transport. With the increases of the normalized rotation speedof the anticyclonic mesoscale eddies relative to the offshore transport, theoffshore current became a meander under the impacts of the anticyclonicmesoscale eddies. The meandered cold tongue and instability front maystimulate the generation of the small-scale eddies. Unidirectional uniformwind along the cold tongue may also contribute to the formation of thesmall-scale eddies.

[学科分类] 地球化学与岩石