Smooth Sheet Bathymetry of the Central Gulf of Alaska

June 28, 2015

While the Alaska Fisheries Science Center (AFSC) has been conducting marine research for decades in Alaskan waters, a lot of basic information about the seafloor, such as depth, is generally not known beyond what is depicted on small scale (1:100,000) NOS (National Ocean Service) navigational charts. Therefore, we have been creating more detailed bathymetry and sediment maps in order to provide a better understanding of how studied animals interact with their environment. Our smooth sheet bathymetry compilation of the central Gulf of Alaska (CGOA) ranged geographically from the Trinity Islands in the west, across the southern coast of Kodiak Island, around the Barren Islands, along the southern Kenai coast, outside of Prince William Sound(PWS), and east and southeastalong the coast to Cape Ommaney, including inlets such as Icy Bay, Yakutat Bay, Lituya Bay, Cross Sound, Salisbury Sound, and Sitka Sound, covering an arc of about 1,400 km of shelf (Fig. 1). The CGOA is a large area covering about 20 degrees of longitude and 4 degrees of latitude, with numerous geomorphic features such as islands, wideinlets,fjords, straits, banks, reefs, glacial troughs and moraines, active tidewater glaciers, fault lines, and shelves both broad and narrow. OurCGOA boundaries are somewhat arbitrary as the CGOA connects to other regions such as the western Gulf of Alaska (GOA), Shelikof Strait, Cook Inlet (Zimmermann and Prescott 2014), interior PWS, the inside waters of Southeast (SE) Alaska, the easternmost portion of the GOA ranging from Cape Ommaney to Dixon Entrance, as well as the open ocean. Our definition of the geographic boundaries was set to match the boundaries of the Gulf of Alaska Integrated Ecosystem Project (GOA-IERP), sponsored by the North Pacific Research Board (NPRB).

The CGOAbathymetryis unevenly and patchily described, with a majority of the smooth sheet surveys conducted prior to World War II (WWII), some shallow areas without any surveys, and some deep areas with detailed surveys. Therefore we combined numerous bathymetric data sources, including smooth sheet surveys, shallow- and deep-water multibeam surveys, and non-hydrographic surveys, to provide coverage across the entire area with as few contradictory overlaps as possible. Minimizing contradictions meant that differences in neighboring soundings could be attributed to seafloor features, several of which, such as the depressions in Kayak Trough, elevations associated with the Fairweather Fault Zone, relic marine terraces around Middleton Island, and fault scarps off Kodiak Island, were revealed in new detail.

Last updated by Alaska Fisheries Science Center on 02/25/2019

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