The northern Gulf of Alaska (GoA) maintains a productive ecosystem, with commercially important fisheries. Virtually all of the many glaciers that line the northern GoA coast are retreating, yet the impacts on the marine ecosystem are poorly understood. This project carried out a set of frequent field observations in a network of tributaries of the Copper River, the single largest source of fresh water to the GoA (and a watershed with substantial glacial coverage). We also carried out a set of research cruises on the continental shelf and slope to the south. Iron is a nutrient that limits biological productivity in parts of the GoA, while nitrate is limiting in nearshore areas. Our work examined the sources of nitrate and iron during different seasons, and their ecosystem responses. Glacier melt impacts transport of bioavailable iron from both rivers and dust, as fine glacial particles are an important source in each case. An additional source is resuspended continental shelf sediments. Dust is transport in the autumn from riverbed sediments from glacierized watersheds by strong winds and transported hundreds of km offshore. Nitrate is known to have a marine source, originating in deep-winter mixing and upwelling. High productivity is observed along the entire coastal transect in spring in response to high concentrations of both nitrate and iron. Climate impacts on the ecosystem will be discussed with the aid of a high-resolution northern GoA coupled physical ecosystem model that incorporates river inputs and oceanographic processes.
For questions about this work, please contact the project's Principal Investigator John Crusius, firstname.lastname@example.org, (206) 543-6978.