New evidence for high discharge to the Chukchi shelf since the Last Glacial Maximum

Jenna C. Hill, University of California - San Diego
Neal W. Driscoll, University of California - San Diego
Julie Brigham_Grette, University of Massachusetts - Amherst
Jeffrey P. Donnelly, Woods Hole Oceanographic Institution
Paul T. Gayes, Coastal Carolina University
Lloyd Keigwin, Woods Hole Oceanographic Institution

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doi.org/10.1016/j.yqres.2007.04.004

Abstract

Using CHIRP subbottom profiling across the Chukchi shelf, offshore NW Alaska, we observed a large incised valley that measures tens of kilometers in width. The valley appears to have been repeatedly excavated during sea level lowering; however, the two most recent incisions appear to have been downcut during the last sea level rise, suggesting an increase in the volume of discharge. Modern drainage from the northwestern Alaskan margin is dominated by small, low-discharge rivers that do not appear to be large enough to have carved the offshore drainage. The renewed downcutting and incision during the deglaciation and consequent base level rise implies there must have been an additional source of discharge. Paleoprecipitation during deglaciation is predicted to be at least 10% less than modern precipitation and thus cannot account for the higher discharge to the shelf. Glacial meltwater is the most likely source for the increased discharge.