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October 27, 2003
Seattle, Washington, USA

Consideration of Permafrost Thaw as a Significant Contributor to Increasing Eurasian Arctic River Discharge

Robert M. Holmes¹, James W. McClelland², Bruce J. Peterson^3
1Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA, 02543, USA, Phone 508-289-7772, Fax 508-457-1548, rholmes@mbl.edu
²The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA, 02543, USA, Phone 508-289-7742, Fax 508-457-1548, jmcclelland@mbl.edu
³The Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA, 02543, USA, Phone 508-289-7484, Fax 508-457-1548, peterson@mbl.edu

Examination of long-term discharge records has shown that the combined discharge from the six largest Eurasian arctic rivers (Yenisey, Lena, Ob', Pechora, Severnaya Dvina, Kolyma) increased 7% from 1936-1999. Thus, these six rivers now contribute on average 128 km³/y more freshwater to the Arctic Ocean now than they did when discharge monitoring began in the 1930's. Projection of arctic river discharge trends into the future, including possible implications for ocean circulation and climate, depend in large part on the causes of the observed increase. Possible explanations for the observed discharge trend include increased precipitation due to global warming, changes in disturbance regimes involving fires and forestry, dam construction and operation, and thawing of permafrost.

Here we focus on the potential role of permafrost thaw as a significant contributor to the observed trend. If permafrost was making a significant contribution to the observed increase in discharge in these large Eurasian arctic rivers, we might expect that watersheds with the most permafrost would show the biggest increase in runoff. No such pattern is apparent. In fact, the river with the most permafrost in its watershed (Kolyma River, 100% permafrost coverage) showed the least change in runoff, whereas the Severnaya Dvina River (with no permafrost in its watershed) had one of the largest increases. Furthermore, increases in active layer depth that would be needed to support the observed increase in discharge (assuming all the thawed water was available for discharge - an unlikely scenario) are large (several meters over the entire 4.3 x 106 km² area of permafrost in these six watersheds), much greater than has been observed. Therefore, we conclude that permafrost thaw is not a significant contributor to the observed long-term increase in Eurasian arctic river discharge.

Abstract Categories: Changes on Land

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