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Effect of sea-level lowering on ELA depression during the LGM

Published online by Cambridge University Press:  20 January 2017

Brian Hanson  and
Roger LeB. Hooke
Brian Hanson*
Affiliation:
Department of Geography, University of Delaware, Newark, DE 19716, USA
Roger LeB. Hooke
Affiliation:
Department of Earth Sciences and Climate Change Institute, University of Maine, Orono, ME 04469, USA
*
⁎Corresponding author. Fax: +1 302 831 6654.
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Abstract

Decreases in equilibrium-line altitudes (ELAs) varied geographically during the last glacial maximum (LGM), with a mid-range value of ~ 900 m commonly deduced from altitude ratio and accumulation–area ratio calculations. Sea level, however, was 120 m lower during the LGM, so the ELA lowering relative to sea level would only be 780 m for a 900-m absolute lowering. With a lapse rate of 0.006°C m−1, this implies a 4.7°C lowering of global temperature. It has been argued that this correction for sea-level change is unnecessary, but the logic on which this is based requires adiabatic compression to apply over much longer time scales than is typically invoked. We find that the correction is necessary. In addition, geometric changes in the atmosphere during the LGM, pointed out by Osmaston (2006), could lead to 0.4°C decrease in the average temperature of the troposphere. Additionally, orographic effects could significantly change the snow distribution on mountain masses near sea level.

Keywords

Last glacial maximum (LGM)Equilibrium-line altitude (ELA)Adiabatic compressionSea-level depression
Type
Short Paper
Information
Quaternary Research , Volume 75 , Issue 3 , May 2011 , pp. 406 - 410
Copyright
University of Washington

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