Toward Long-Term Oceanographic Monitoring of the Gulf of Alaska Ecosystem

Interannual variations in Gulf of Alaska shelf temperature and salinity could significantly influence this ecosystem and hence the recovery and restoration of organisms and services affected by the Exxon Valdez oil spill. This variability is being quantified from time series at hydrographic station GAK 1, near Seward Alaska, and within the Alaska Coastal Current. Data from this station spans a 32 year period. In addition to maintaining the sampling, this project has extended the value of these time series by developing predictions for the freshwater content, and the baroclinic components of the mass and freshwater transport within the Alaska Coastal Current. The results allow us to hindcast these variables back to 1948 and therefore provide a data set that can be used in retrospective studies of this marine ecosystem. We have also generated a surrogate time series of freshwater runoff for the Gulf of Alaska based on atmospheric sea level pressure differences between Ketchikan and Seward. This surrogate time series allows us to extend the freshwater discharge record back to 1900. This surrogate time series should be of considerable interest to investigators seeking to understand interdecadal climate variability in the Gulf of Alaska. We have also attempted to relate Seward sea level variations to GAK 1 dynamic height variability. This effort has been partially successful but there are other (as yet unidentified) contributions to sea level variability here. Thus at this time, Seward sea level variations cannot be used as a predictor of dynamic height (salinity) variations for the northern Gulf of Alaska.