Interannual variability of summer biochemical enhancement in relation to mesoscale eddies at the shelf break in the vicinity of the Pribilof Islands, Bering Sea

Abstract

Abstract This study examined variability of the eddy field and primary production over the Bering Sea's eastern shelf break area during summer using a satellite multi-sensor data set. The eddy field and on-shelf nutrient flux below 50 m water depth were also investigated using a numerical model. The satellite-altimeter data analysis and numerical experiments indicated that the eddy field was induced by perturbations of the Bering Slope Current system and/or instabilities in the Bering Sea basin via flow through the Aleutian passes. The distribution of high primary production roughly coincided with the high variability area of the eddy field. Numerical experiments showed a 70% increase in net on-shelf flux and 54% increase in net on-shelf transport by the generation/propagation of eddies along the shelf break. At Pribilof Canyon, towed CTD/fluorometer measurements during the summer of 2003 revealed a stable water column and high fluorescence (>10 μg L −1 ) in the area between the 200- and 1000-m isobaths at a time when there was a low level of on-shelf flux regardless of the eddy field. Conversely, the eddy-induced, on-shelf flux and stable water column can enhance primary production from spring to summer at the shelf break. Moreover, the eddy-induced on-shelf nutrient flux probably contributes to the primary productivity at the western shelf of the Pribilof Islands where the Bering Sea ecosystem is very dynamic. This eddy-related shelf break process can be applied to not only the Bering Sea shelf break but also all shelf break areas in which propagating eddies are found.