Formation of a basin‐scale surface chlorophyll pattern by Rossby waves

The enhancement of surface chlorophyll by Rossby waves, which has recently been detected in bandpass‐filtered ocean color data [Cipollini et al., 2001; Uz et al., 2001], is shown to be intense enough to form a dominant pattern in monthly mean basin‐scale ocean color satellite maps of the Indian Ocean. Results from a biological‐physical coupled model suggest that this phenomenon, which is visible predominantly in austral winter, is caused by Rossby‐wave induced upwelling that lifts the deep chlorophyll maximum (DCM) into contact with the surface mixed layer (ML). The model results suggest that these events are not associated with any significant input of nutrients into the ML. While the temporal enhancement of regional primary production by Rossby waves is substantial (∼30%), it is not necessarily associated with a corresponding increase in surface chlorophyll, e.g., when the ML is too shallow to touch the DCM, and may hence escape detectability by satellite measurements.