Programmatic structure

The BEST-BSIERP program (http://bsierp.nprb.org/) is designed to provide the understanding of the Bering shelf ecosystem necessary to anticipate its future trajectory under scenarios of climate variability, particularly one of a changing sea ice regime. Through an extensive field program, it will contribute to the development of a series of vertically integrated models, while supporting additional competing modeling projects that will inform the integrated model (Fig. 1).

The models are anchored in the physics of the system. The modelers will begin by identifying general circulation models (GCMs) that best reproduce 20th century conditions in the Bering Sea region. Ensemble runs from these models under IPCC AR4 scenarios will be used to initialize and force a ROMS (Regional Ocean Modeling System) model of the Bering Sea with 10 km resolution everywhere and 3 km resolution over the eastern Bering Sea shelf. The model includes a new sea ice model that combines an elastic-viscous-plastic rheology and a one-layer ice and snow thermodynamics model. Nutrient-phytoplankton-zooplankton-detritus (NPZ-D) models will be embedded within the ROMS modeling framework.

A parallel physical model is also being developed. This model, which does not include biology, results from coupling a POP (Parallel Ocean Program) ocean model to a complicated dynamic-thermodynamic ice model that utilizes 12 categories of undeformed ice, ridged ice, ice enthalpy, and snow. It explicitly simulates sea ice ridging based on ice deformation without causing excessive buildup of ice thickness, an important aspect for a region where ice is thin and easily diverges and converges. The curvilinear grid averages 7 km in resolution, but reaches a resolution of 2 km near the Alaskan coast. It extends south to 35o N,

Fig. 1. Conceptual diagram of the ecosystem structure to be studied by BEST-BSIERP through integrated field and modeling efforts.

where it is nested within a 0.65o global model. It is forced by reanalysis products (NCAR/NCEP and ECMWF ERA40). As with the ROMS model, tides are included. The main goal of the project is accurate understanding of the dynamics responsible for the observed ocean and ice conditions during the coordinated field programs.

The nutrient-phytoplankton-zooplankton-detritus model, including benthic secondary production, within the ROMS model focuses on the lower trophic levels. This model is coupled to an energy flow model of forage fish and euphausiid abundance in space and time (FEAST). The model includes behavior rules calibrated against field observations. It allows for local depletion of primary and secondary production, thus accommodating both bottom-up and top-down control. Scenarios of changing predation from above will be included, as will loss to commercial fishing through economic models of the fishing industry.

In parallel with this integrated model, investigators are supported to develop a behavioral model of predation pressures on forage fish by piscivorous fish, birds, and marine mammals. Simultaneously other investigators will use historical data to develop a correlative multispecies biomass dynamics model including climate effects.

The field portion of the program is designed to provide a description of the Bering Sea ecosystem at different times of the year during consecutive years. While the field data will not provide an estimate of temporal trends of the structure of the ecosystem, comparison with historical data may allow such an estimate to be made. Furthermore, by providing data for model calibration and validation, it is anticipated that the models mentioned above, when forced with future climate scenarios may allow estimation of the trajectory of the ecosystem and its impact on the local human population.

The field program will be supported by a series of process study cruises, survey cruises, and some cruises which combine the two activities. The state of the water column will be sampled on all cruises to provide core physical and chemical data to the participants. Moorings will provide time series of the physical and biological parameters characterizing the water column. The import of iron in sea ice on the development of the spring bloom is also considered. Individual projects have been supported to calibrate and apply new chemical techniques for the estimation of primary production in the water column, as well as the role of ice algae in the food chain. Projects have also been supported to describe the plankton community structure and associated rates to be used in constraining models. Studies of the benthos include estimation of both community structure and rates of nutrient regeneration. One project is devoted to jellyfish population dynamics. A number of projects study aspects of the ecology of pollock, cod, and arrowtooth flounder. These include the time-varying distribution of the organisms as measured by multiple techniques, their diet, and seasonal energetics. Whales, walruses, and fur seals are the subject of another large suite of projects dealing with distribution, diet, reproductive success, and response to prey persistence. Seabirds are the topic area for another set of focused studies, particularly the thick billed murre and black legged kittiwake. These studies involve both distribution and assessment of the stress level of the birds in response to variable food resources.

Finally, a series of human dimensions projects have been supported at six different communities around the Bering Sea. These communities were selected because of their unique relationships with the Bering Sea ecosystem.

Both BEST and BSIERP have supported data management projects. These are coordinating the data formats and mirroring each other's holdings so that data access is transparent to the PIs involved in the program. Data is expected to be available to all members of the program within 1 year of collection. Ultimately, data will be deposited in national data archives.

The first BEST cruise took place during the summer of 2007 with a restricted suite of funded projects. Multiple cruises are completed or planned for 2008, 2009, and 2010. The US Coast Guard icebreaker Healy is the planned research platform when the water is ice-covered in spring. Healy and a series of non-ice-strengthened ships are scheduled for sampling cruises during the summer and early fall. While berths are at a premium on the cruises, particularly the icebreaker cruises, unfunded collaborators are welcome on a 'not-to-interfere' basis when an unused berth is available. Oceanographers from Ocean University of China in Qingdao and University of Oldenburg accompanied a recent cruise. Berths are also a priority for outreach and educational activities. All cruises, thus far, have included one or more teachers who maintained blogs for their classes and the general public. The media have accompanied the ships. Stops have been made in native communities allowing tours of the ship and presentations concerning the studies. On occasion, a community member has accompanied the ship for a short survey leg.

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