Multibeam bathymetric and sediment profiler evidence for ice grounding on the Chukchi Borderland, Arctic Ocean

Multibearn bathymetry and 3.5-kHz sub-bottoin profiler data collected from the US icebreaker Healy in 2003 provide convincing evidence for grounded ice on the Chukchi Borderland off the northern Alaskan margin, Arctic Ocean. The data show parallel, glacially induced seafloor scours, or grooves, and intervening ridges that reach widths of 1000 in (rim to rim) and as much as 40 m relief. Following previous authors, we refer to these features as "megascale glacial lineations (MSGLs)." Additional support for ice garounding is apparent from stratigraphic unconformities, interpreted to have been caused by ice-induced erosion. Most likely, the observed sea-floor features represent evidence for massive ice-shelf grounding. The general ESE/WNW direction of the MSGLs, together with sediment, evidently bulldozed off the Chukchi Plateau, that is mapped on the western (Siberian) side of the plateau, suggests ice flow from the Canada Basin side of Chukchi Borderland. Two separate generations of glacially derived MSGLs are identified oil the Chukchi Borderland from the Healy; geophysical data. The deepest and oldest extensive MSGLs appear to be draped by sediments less than 5 in thick, 1,whereas no sediment drape call be distinguished within the resolution of the sub-bottom profiles oil the younger generation. (c) 2005 University of Washington. All rights reserved.