GLOBEC 2000: Nested interdisciplinary models for the Gulf of Alaska
D. Haidvogel (Rutgers University), A. Hermann (Pacific Marine Environmental Laboratory), S. Hinckley (Alaska Fisheries Science Center), P. Stabeno (Pacific Marine Environmental Laboratory)

The proposed work will significantly augment an ongoing GLOBEC-funded interdisciplinary modeling effort for the Coastal Gulf of Alaska. Technical objectives include: higher spatial resolution and nested grid capabilities for regional circulation modeling, nested mesoscale atmospheric modeling for 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, proposed under this AO by Dr. Peter Rand. 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. This comparison will help elucidate the observed (inverse) covariance of salmon in the two systems on decadal time scales.

Central scientific issues include the following:

1. The "optimal stability window" hypothesis: Gargett (1997) 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. In Gargett's hypothesis, there exists an "optimal window" of stability for each area, which yields greatest primary production with optimal levels of both nutrients and light. Shifts in the Aleutian Low, with associated changes in coastal runoff and winds, yield greater/lesser production in the two areas, producing the observed covariance between northern and southern stocks. The links in this chain of causality will be probed directly through continuous, multi-decadal simulations with a suite of coupled models (circulation- NPZ-salmon) of the CGOA, and contrasted with parallel GLOBEC-funded efforts in the CCS.
2. The source of nutrients to the CGOA: 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. At the same time, a coastal NPZ model, calibrated with CGOA data and run in 1-D mode, suggests a severe depletion of nutrients without some lateral supply. It is suggested that surface Ekman flux from the adjacent subarctic gyre may account for much of the required nutrient flux. This hypothesis will be tested by diagnosing the output from the multi-decadal runs.

DATA COLLECTION DETAILS

This page was last updated on September 25, 2000.

Maintained by:
Hal Batchelder [hbatchelder@coas.oregonstate.edu
College of Oceanic & Atmospheric Sciences
Oregon State University
Corvallis, OR 97331-5503
phone: 541-737-4500; FAX 541-737-2064