This core retrospective modeling and data assimilation project addresses broad GLOBEC program goals, in addition to the more tightly focused aims of the Northeast Pacific (NEP) GLOBEC program in the Coastal Gulf of Alaska (CGOA). This work aims to elucidate mechanisms that influence the observed production at multiple trophic levels (phytoplankton, zooplankton, and pink salmon) in the CGOA. Specific goals are to: (i) quantify how physical features in the CGOA and variability related to climate change impact zooplankton biomass, production, distribution, and the retention and loss of zooplankton from coastal regions; (ii) quantify the impact of key coastal physical and biological processes, such as freshwater runoff and cross-shelf transport; and (iii) compare the impacts of climate variability and change (such as El Nino-La Nina cycles and regime shifts) on marine animal populations (pink salmon) in the CGOA. The coupled models employ advanced data assimilation techniques to produce optimal merged data/model products, which will be delivered online for use by the GLOBEC NEP-CGOA synthesis effort.
End-products include: 1) Synthesis of GLOBEC-CGOA field data through explicit, adjoint based, 3D physical data assimilation into nested circulation models; 2) Application of these improved circulation fields to lower trophic level (NPZ) simulations which include salmon prey items; 3) Development of an adjoint version of the combined circulation-NPZ model, for formal exploration of the sensitivities of derived indices to forcing functions; 4) Production of physical, NPZ, and salmon hindcasts of years with significant interannual climate variability, delivered online for use by other GLOBEC synthesis research programs and models; 5) Production of circulation and prey fields for an Individual-Based Model of pink salmon; 6) Implementation of an Eulerian model of pink salmon with other NPZ components; 7) Assimilation of CGOA biological field data into 1D NPZ models with adjoint techniques; 8) Development of an NPZ model suitable for the Northeast Pacific, to examine spatial patterns of response to climate variability; 9) Visualization of Eulerian and Lagrangian model results with online, interactive, immersive display technologies.
The data assimilation and hindcast activities will benefit NOAA's Fisheries and the Environment (FATE) program, which is concerned with effective biophysical indices and other Fisheries Oceanography programs in the CGOA which require accurate circulation and NPZ hindcasts for retrospective studies. The data assimilation and sensitivity issues will contribute to the Alaska Ocean Observing System (AOOS) program. Multiple Ph.D. scientists and students will be trained. Educational outreach will take place via novel visualization techniques to display 3D model results.