Stratification on the Bering Shelf and its Consequences for Nutrients and the Ecosystem: The Effects of Ice and Coastal Water Advection

Funds are provided to study the impact of physical variability on the processes and structure of the Bering shelf ecosystem, with special emphasis on how freshwater redistributed by the shelf circulation or introduced from sea ice melt modifies stratification and nutrient distributions. The principal investigators inquire how changes in sea ice affect advection and mixing; how variable fluxes of low-salinity, nutrient-deficient coastal waters may affect production; how cross-shelf fluxes are established and altered; how these fluxes might respond to climate change; how the seasonal stratification cycle is controlled; and how the buoyant coastal flow evolves.

The 2008-2010 field effort will focus on the central Bering Sea shelf and will employ both hydrography, including extensive d18O sampling, and a nine-mooring array that spans most of the central shelf. The moorings variously will carry ADCPs, T/C recorders, fluorometers, and temperature chains. The measurements will be augmented by hydrographic and d18O sampling and drifter studies under other support. Analysis will also incorporate wind forcing, coastal discharges, surface buoyancy fluxes, and ice thickness and drift into the synthesized data set and its interpretation.

These data, in conjunction with another mooring program funded elsewhere, will provide much of the background circulation and stratification information necessary to place the biological data from BEST in context.