The Last Glacial Maximum
Peter U. Clark,1,*
Arthur S. Dyke,2
Jeremy D. Shakun,1
Anders E. Carlson,3
Jorie Clark,1
Barbara Wohlfarth,4
Jerry X. Mitrovica,5
Steven W. Hostetler,6
A. Marshall McCabe7
We used 5704
14C,
10Be, and
3He ages that span the interval
from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the
timing of the Last Glacial Maximum (LGM) in terms of global
ice-sheet and mountain-glacier extent. Growth of the ice sheets
to their maximum positions occurred between 33.0 and 26.5 ka
in response to climate forcing from decreases in northern summer
insolation, tropical Pacific sea surface temperatures, and atmospheric
CO
2. Nearly all ice sheets were at their LGM positions from
26.5 ka to 19 to 20 ka, corresponding to minima in these forcings.
The onset of Northern Hemisphere deglaciation 19 to 20 ka was
induced by an increase in northern summer insolation, providing
the source for an abrupt rise in sea level. The onset of deglaciation
of the West Antarctic Ice Sheet occurred between 14 and 15 ka,
consistent with evidence that this was the primary source for
an abrupt rise in sea level ~14.5 ka.
2 Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada.
3 Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA.
4 Department of Geology and Geochemistry, Stockholm University, SE-10691, Stockholm, Sweden.
5 Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
6 U.S. Geological Survey, Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
7 School of Environmental Science, University of Ulster, Coleraine, County Londonderry, BT52 1SA, UK.
* To whom correspondence should be addressed. E-mail: clarkp{at}onid.orst.edu
