Seafloor Surveys Provide Circum-Basin Evidence for Thick Pleistocene Ice in the Arctic Ocean

In 1998 and 1999 a U.S. Navy nuclear-powered submarine was used to collect swath bathymetry and sidescan data for the Arctic Basin as part of the SCICEX program. Data collected over Chukchi Borderland and Lomonosov Ridge revealed glacially-formed erosion and sculpting of the seafloor at water depths of several hundred meters. These results provided key evidence that very thick floating ice sheets (ice shelves) or densely packed armadas of table icebergs had covered portions or perhaps the entirety of the Arctic Ocean at some time intervals during the Pleistocene [Polyak et al., 2001]. At the time of this revelation, opportunistically collected SCICEX swath data for other shallow regions (< 1000 m) in the Arctic Basin had not yet been processed. Here we present a compendium of glacigenic features imaged in the Arctic using the SCICEX swath-mapping system. In addition to the published findings for Lomonosov Ridge and Chukchi Plateau, the data show new evidence for grounded ice on Yermak Plateau, Northwind Ridge and the Alaska Margin in the depth range of 300 to 1000 m. We characterize the orientation, depth, and extent of observed glacigenic features and document their three-dimensional morphology. Where possible, the swath topography is supplemented by high-resolution subbottom profiler data to create a volumetric representation of erosion. These two- and three-dimensional maps of ice contact features have been used to constrain the provenance and relative timing of arctic ice sheets. Multiple fields of glacigenic lineations (flutes) observed on Northwind Ridge and Chukchi Plateau are similar in strike, trending NNW. Polyak et al. [2001] inferred that these features had been formed by ice originating from the Canadian Arctic Archipelago. The discovery of flutes on the Alaska margin oriented parallel to the shelf break supports this prediction. This pattern of the spatial distribution of glacigenic bedforms suggests that ice shelves from the Canadian Arctic Archipelago extended more than 1000 km, covering much, if not all, of the Amerasia Basin. Ice shelves in the Eurasia Basin achieved comparable size based on the erosion documented on Lomonosov Ridge, which indicates ice moving from the Barents/Kara continental margin. Pending investigation of temporal relationships between glacigenic bedforms from various parts of the Arctic and future mapping of other shallow features will provide a comprehensive history of thick-ice events in the Arctic Ocean.