GLOBEC 2000: Nested Interdisciplinary Models for the Gulf of Alaska

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As part of an ongoing GLOBEC-funded interdisciplinary modeling effort for the Coastal Gulf of Alaska, this study includes the following technical objectives: higher spatial resolution and nested grid capabilities for regional circulation modeling, nested mesoscale atmospheric modeling and regional wind and buoyancy forcing, and a deep-ocean NPZ model to provide boundary conditions for an existing coastal NPZ model. Present single-year simulations of these models will be expanded to continuous multi-decadal integrations, designed to provide circulation and prey fields to an individual-based model of juvenile salmon. Together, these coupled models will be used to explore the mechanisms by which interannual/interdecadal variability of physical fields affect the production of GLOBEC target zooplankton species and the feeding of juvenile salmon in the CGOA. The ecosystem dynamics of these models will be compared with those developed under GLOBEC for the California Current System. Central scientific issues include: 1) The "optimal stability window" hypothesis where Gargett has suggested that variations in the Aleutian Low affect salmon through their impact on water column stability in the CGOA and CCS systems. Typically, high nutrient but low light conditions are observed in the subarctic gyre adjacent to the CGOA, in contrast to low nutrient but high light conditions in the subtropical gyre adjacent to the CCS. And 2) The source of nutrients of the CGOA, i.e., the Coastal Gulf Alaska is a downwelling system for nearly all of the year. The adverse pressure gradient so produced should work against the supply of deep nutrients to the shelf, whether that shelf is smooth and straight or (as is the case in the CGOA) punctuated by submarine canyons. These comparison will help elucidate the observed (inverse) covariance of salmon in the two systems on decadal time scales.