AFSC/RACE/GAP/ZIMMERMANN: Bathymetry: western Gulf of Alaska Grid

We defined the bathymetry of Shelikof Strait and the western Gulf of Alaska (WGOA) from the edges of the land masses down to about 7,000 m deep in the Aleutian Trench. We made this map by combining soundings from historical National Ocean Service (NOS) smooth sheets (2.7 million soundings); shallow multibeam and LIDAR (Light Detection and Ranging) data sets from the NOS and others (subsampled to 2.6 million soundings); and deep multibeam (subsampled to 3.3 million soundings), single-beam, and underway files from fisheries research cruises (9.1 million soundings). The legacy smooth sheet data, some over a century old, was the best descriptor of much of the shallower and inshore areas, but it was superseded by the newer multibeam and LIDAR, where available. Much of the offshore area was only described by non-hydrographic single-beam and underway files. We carefully combined these disparate data sets in an attempt to preserve seafloor features for research purposes. We also attempted to minimize bathymetric data errors so that they would not create artificial seafloor features that might impact such analyses. The main result of the bathymetry compilation is that we observe abundant features related to glaciation of the shelf of Alaska during the Last Glacial Maximum including abundant end moraines, some lateral moraines, glacial scour marks, eskers, iceberg keel marks, and two types of pock marks. We developed an integrated onshore-offshore geomorphic map of the region that includes glacial flow directions, glacial moraines, and iceberg keel marks to better define the extent of late Quaternary glaciations.