Funds are provided to achieve three major goals. 1. To synthesize data from the BEST-BSIERP coordinated programs in the Bering Sea and data from other sources, collected during the same time period (2007-2010), via modeling and data assimilation. Two joint data assimilation systems will be applied to reconstruct the physical oceanographic fields of the eastern Bering ice-ocean system. The first system will be configured to reconstruct the large-scale circulation in the eastern Bering Sea and to accurately describe the large-scale processes in the South Eastern Bering Sea Shelf. The second will be configured for the eastern Bering Sea Shelf and will explicitly resolve eddy and tidal dynamics, thus leading to a better understanding of the nonlinear interaction processes between the deep basin and the shelf region of the eastern Bering Sea. 2. To analyze the reconstructed fields and identify processes important for causing observed variability. 3. To determine the impact of assimilating data with different origins on the estimation of near-surface transports of volume, momentum, heat, and material. This will be accomplished through adjoint sensitivity analysis. Results will help optimize Bering Sea mooring observations in future studies.
The Bering Sea is the largest commercial and subsistence fishery of the United States. Management of this fishery in the face of ongoing climate variability requires an understanding of all the processes impacting the fishery. Amongst these are the changing water temperature, which influences the growth rate of fish, and the current field, which carries fish eggs and larvae from their spawning regions to their nursery grounds. This project will contribute to an understanding of how these fields change in response to other external forcing.
Dominant ocean variability in high-latitude seas, including the Bering Sea, happens on relatively small scales, with coastal currents as narrow as 20 km. These currents may become unstable, with generation of energetic eddies of the same spatial scale. In this project we have developed a high-resolution, three-dimensional computer model of the Eastern Bering Sea that reproduces and allows studying these features. It allowed us to see how the 2000x2000 km remote area of the global ocean, very important to biodiversity and US economy, operates and how different regions (island passes, shelf slope, shelf, interior ocean) are interconnected. Using our model simulations, we have learned that variability in volume transports all major passes in the Aleutian Islands varies on a 2-week scale. This variability is supported by tidal mixing in the passes and over the slopes. There is more mixing, and stronger transports when the two diurnal tide components (lunar and solar) are in phase. Following the periods of intensified currents, the model shows that eddies pinch off regularly in the area of Bering Canyon. It is plausible (and will be further investigated) that these eddies help transport fish larvae onto the wide and shallow Bering Sea shelf, on the way from spawning to settling locations. Energetic and copmlex flows in the Eastern Sea area are best presented in flow animations developed by our group and available online at: http://ingria.coas.oregonstate.edu/news/Amukta_pass.html http://ingria.coas.oregonstate.edu/news/Bering.html http://ingria.coas.oregonstate.edu/bering_canyon_ssh.html