Funds are provided to model the physics and ecosystem structure of the Bering Sea. Change in climate forcing will be determined from coupled atmosphere-ocean general circulation model (GCM) simulations made for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). The twentieth century hindcasts from these models differ in terms of their ability to replicate past observed conditions; a subset of the better models will be used to project the trends, variability and uncertainty of the climate of the Bering Sea through the first half of the 21st century. This ensemble of GCM model results will be used primarily for dynamical downscaling, i.e., as initial and boundary conditions for high-resolution ocean model experiments with the Regional Ocean Modeling System (ROMS). The ROMS simulations are designed to properly handle physical processes known to be important on the Bering Sea shelf, such as sea ice, tides, and cross-shelf exchange; these results will form the direct input for embedded spatially-explicit nutrient-phytoplankton-zooplankton (NPZ) and food web model experiments.
This project is part of a larger program designed to develop understanding of the integrated ecosystem of the eastern Bering Sea shelf, a highly productive region of US coastal waters. This ecosystem is home to a major portion of the commercial fisheries of the US and also provides significant resources to subsistence hunters and fisherman of Alaska. The model will help to synthesize our current and developing understanding of how this system functions.
The South East Bering Sea plankton community can be characterized by large and small phytoplankton, microzooplankton, large and small copepods, and euphausiids. An NPZD model developed by S. Hinckley for the Gulf of Alaska with a subarctic ecosystem structure comprising multiple nutrient, phytoplankton, and zooplankton components therefore provided a convenient starting point for the development of the BEST-NPZD model. To adapt the model to the Eastern Bering Sea ecosystem, the model was coupled at the ocean surface to an ice biology module and at the ocean floor to a benthic biology module. A pelagic jellyfish component was also added, and some of the formulations were modified to better describe the Bering Sea ecosystem dynamics. The pertinent changes are outlined in Gibson and Spitz (2011). A schematic of the BEST-NPZD model is shown in the attached figure. The model was developed, then tested in a 1-D configuration, finding optimal values for the unknown parameters. It was then applied to a 3-D model of the Bering Sea where it was validated against the observations. Finally, it was run to evaluate differences between "warm" and "cold" years. These results will be coming out shortly in various publications. Hunt, G.L., Jr., P. H. Ressler, A. De Robertis, K. Aydin, G. Gibson, M.,Sigler, I. Ortiz, E. Lessard, B. Williams, A. Pinchuk, and T. Buckley. (In revision). Euphausiids in the Eastern Bering Sea: A synthesis of recent studies of euphausiid production, consumption and population control. Deep-Sea Research II. Gibson, G. A. Hermann, A. J., Hedstrom, K., Curchitser. E. N. (In revision). Response of Euphausiid production to ‘cold’ and ‘warm’ years in the Bering Sea. Deep-Sea Research II. Hermann, A. J., Gibson, G. A., Bond, N. A., Curchitser, E. N., Hedstrom, K., Cheng, W., Wang, M., Stabeno, P. J., Eisner L., Janout, M., (2013). A multivariate analysis of observed and modeled biophysical variability on the Bering Sea shelf: multidecadal hindcasts (1969-2009) and forecasts (2010-2040). Deep Sea Research II: Topical Studies in Oceanography.
