Wednesday, 6 August 2003: 3:45 PM
Variability in shelf transport in the Gulf of Alaska, Part I: Diagnosis of air-sea interactions
This paper represents an overview of a project focused on how interannual fluctuations in atmospheric forcing result in variations in along-shore and cross-shelf transports in the northern Gulf of Alaska (GOA). These transports appear to be important to to the survival of juvenile salmon, through their impacts on advection to favorable nursery grounds, and on availability of suitable prey. The approach has been to carry out a coordinated program of in situ observations and numerical atmosphere and ocean modeling. Previous observational and modeling results indicate the importance of local winds over the shelf to its primary current system, the Alaska Coastal Current (ACC). Direct observations of these winds are insufficient for real-time and retrospective analyses. As detailed in Part II of this series of papers, a mesoscale numerical weather prediction model, the MM5, has been employed to downscale from the coarse grid provided by the NCEP/NCAR Reanalysis data set. The output from the MM5 has been used to assess various aspects of the atmospheric forcing: the variability in surface heat fluxes versus momentum fluxes, the characteristic patterns of mean wind stress over the shelf, the importance of localized versus distributed freshwater runoff, and the relative roles of the local atmospheric forcing to that over the deep basin of the GOA. This output has also been used as boundary conditions for simulations using the Regional Ocean Modeling System (ROMS), as detailed in Part IV of this series of papers.