JISAO Researchers Offer New Insights into Productivity of Coastal Gulf of Alaska

Oceanographers have long wondered how the coastal Gulf of Alaska supports such large populations of fish, seabirds and marine mammals, despite ecological conditions that would suggest otherwise. Ambient winds in this region cause coastal downwelling – where the surface layer of warm, nutrient-deficient water thickens and sinks – generally resulting in low nutrient concentrations and limited growth of phytoplankton comprising the base of the food web. Under the lead of Albert Hermann, researchers at the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) and NOAA’s Pacific Marine Environmental Laboratory (PMEL) have developed a coupled physical-biological computer model for coastal Gulf of Alaska to explain and quantify the mechanisms responsible for supplying nutrients from depth to shallow regions where they can be exploited by phytoplankton. The model simulations reveal high nutrient concentrations in “rivers” along the flanks of underwater canyons and in “fountains” over shallow banks due to the effects of tides. Moreover, wind patterns attributable to the prominent terrain encircling the Gulf of Alaska promote the upwelling of nutrients in a strip offshore of the coast at a rate greater than with the downwelling near the shore.

Background: The results of this research are detailed in an upcoming article in the journal Progress in Oceanography. It is one of seven papers submitted to a special edition entitled Deep-Sea Research II on the Northeast Pacific that include contributions from JISAO and PMEL scientists. This research was carried out in conjunction with the U.S. Global Ocean Ecosystems Dynamics (GLOBEC) program with the support of NOAA’s Center for Sponsored Coastal Ocean Research (Project Manager: Elizabeth Turner). More information on the GLOBEC program is available at http://www.usglobec.org.

Significance: Improved modeling efforts, such as those described here, will notably enhance our scientific understanding of the relationships between the marine environment and the survival of commercially valuable fish in the western Gulf of Alaska. Walleye pollock (Theragra chalcogramma) was the first fish species examined in these studies, but the program has since evolved to encompass the study of the ecosystems of the North Pacific Ocean and Bering Sea with the goals of improving understanding of ecosystem dynamics and applying that understanding to the management of marine resources. This research supports NOAA Mission Goal 1 – Protect, Restore, and Manage the Use of Coastal and Ocean Resources through an Ecosystem Approach to Management.