Variability of Bering Sea eddies and primary productivity along the shelf edge during 1998–2000 using satellite multisensor remote sensing

TOPEX/Poseidon sea surface height anomalies (SSHAs), Sea-viewing WIde Field-of-view Sensor (SeaWiFS) L3 chlorophyll a (chl-a) concentration, and primary production were examined to determine the relationship between an eddy field and primary productivity along the shelf edge in the southeastern Bering Sea. Primary production was calculated from SeaWiFS chl-a, photosynthetically active radiation (PAR), and AVHRR sea surface temperature (SST) data using the vertically generalized production model (VGPM).A time–latitude plot of SSHAs, which was derived from TOPEX/Poseidon ground track D-79 along the shelf edge, described the northwestward propagation of positive SSHAs (indicating an anticyclonic eddy) and negative SSHAs (indicating a cyclonic eddy staying near Zhemchug Canyon or over the deep basin). There were increases in the variability of the SSHA field and the speed of eddy propagation during 2000 along the shelf edge. Time–latitude plots of SeaWiFS chl-a exhibited relatively high chl-a (over 1.0 mg m-3) along the shelf edge for 2–3 months in the summer of 1999, when there was low eddy activity, and for about 6 months in 2000, when there was an eddy-rich environment. The same pattern of chl-a appeared in time–latitude plots of primary production. Monthly averaged primary production along the shelf edge was 20.88, 18.37, and 24.04 g C m-2 month-1 in 1998, 1999, and 2000, respectively. Primary production decreased from about 28 g C m-2 month-1 (June) to about 18 g C m-2 month-1 (July) in 1999; however, about 25 g C m-2 month-1 of primary production was maintained from June to September in 2000. These results indicate a positive correlation between the variability in the Bering Slope Current (BSC) eddy field and primary production along the Bering Sea shelf edge. An increase in the BSC transport and the eddy field fluctuation contributed to the vertical nutrient supply to the subsurface layer and shelf–slope exchange, thereby maintaining high primary productivity along the shelf edge of the southeastern Bering Sea in 2000. [Copyright &y& Elsevier]