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

Published online by Cambridge University Press:  20 January 2017

Jenna C. Hill*
Affiliation:
Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0208, USA
Neal W. Driscoll
Affiliation:
Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0208, USA
Julie Brigham-Grette
Affiliation:
Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USA
Jeffrey P. Donnelly
Affiliation:
Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
Paul T. Gayes
Affiliation:
Center for Marine and Wetlands Studies, Coastal Carolina University, Conway, SC 29526, USA
Lloyd Keigwin
Affiliation:
Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
*
*Corresponding author. Fax: +1 858 534 3310.E-mail address:[email protected] (J.C. Hill).

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.

Type
Research Article
Copyright
University of Washington

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