Phytoplankton patchiness indicates the fluctuation spectrum of mesoscale oceanic structure

Abstract

Satellite imagery and large-scale oceanic experiments have replaced traditional concepts of broad sluggish currents moving throughout the ocean by the concept of a continuous distribution of more energetic eddies, the dominant eddies having space scales^1,2 of the order of 100 km. Near the ocean boundaries in such areas as the Gulf Stream and the California Current, these eddies exhibit strong thermal contrast, of the order of 2–6 °C, and their structure and distribution can be mapped using satellite thermal IR imagery^3,4. Over most of the ocean, however, the thermal contrasts are much lower, of the order of 0.1–0.5 °C, and tend to be masked from satellite observation by small-scale atmospheric variations. To map the structure associated with mesoscale horizontal water motions in these areas, another indicator must be used for observation from space. We present here the first results of spectral analysis of satellite imagery of what we believe is phytoplankton patchiness controlled by mesoscale (10–100 km) water motions.