Site: Northern Gulf of Alaska

Credit: Russ Hopcroft

The coastal Gulf of Alaska water column is becoming progressively more stratified — the entire water column is warming, but more rapidly at the surface than near the seafloor, while near surface waters are becoming fresher. This is due to multiple factors including the air-sea heat flux, ocean heat flux convergences, the stabilizing influence of runoff, the destabilizing effects of cooling and vertical mixing, and the wind driven cross-shelf buoyancy flux. Stratification impacts the water column mixing in winter that helps reset the shelf for the next season’s biological production. Therefore, the concentration and composition of the phyto- and zooplankton community shows direct and indirect connections to the thermal conditions of the Gulf of Alaska shelf. These far reaching implications for upper trophic levels could only be detected using a high quality, multi-decade dataset.