Phytoplankton distribution as observed from bio-optical drifters and SeaWiFS images in the Bering Sea green belt

Abstract

Bering Sea green belt is characterized by high productive region, with interactions of cyclonic and anti-cyclonic eddies. To study temporal and spatial variability of phytoplankton, we deployed two bio-optical drifters in a clockwise eddy in 2001 and 2002. The drifters were equipped with a spectroradiometer to measure upwelling radiance as same as Sea Wide Field-of-view Sensor (SeaWiFS) wavelength. SeaWiFS images were employed to monitor the spatial pattern of chlorophyll-a (chl-a). The drifter also measured sea surface temperature (SST). We compared SST with TOPEX/POSEIDON sea surface anomaly data and analyzed time and scale correlation of SST and phytoplankton distribution in some eddies. In 2001, a clockwise eddy trapped the drifter for 10 days. It represented relatively high chl-a concentration (about 1.0 mg m^-3) and low SST (about 8.5°C). After that it drifted to the Bering Sea slope current region along the shelf edge, and observed among 20 days. In 2002 we deployed a drifter in center of clockwise eddy, it was staying in this eddy for 14 days. There represented relatively low chl-a concentration (about 0.4 mg m^-3) and high SST (about 9.5°C). After that it drifted along Bering slope current similarly. The phytoplankton distribution was deferent from two years in spite of same kind of anti-cyclonic eddy. These deferent might be depending on deference of eddy's life stage.