Collapse of the California Current During Glacial Maxima Linked to Climate Change on Land
T. D. Herbert,1*
J. D. Schuffert,1
D. Andreasen,2
L. Heusser,3
M. Lyle,4
A. Mix,5
A. C. Ravelo,2
L. D. Stott,6
J. C. Herguera7
Time series of alkenone unsaturation indices gathered along the
California margin reveal large (4° to 8°C) glacial-interglacial changes in sea surface temperature (SST) over the past 550,000 years. Interglacial times with SSTs equal to or exceeding that of the
Holocene contain peak abundances in the pollen of redwood, the
distinctive component of the temperate rainforest of the northwest coast of California. In the region now dominated by the California Current, SSTs warmed 10,000 to 15,000 years in advance of deglaciation at each of the past five glacial maxima. SSTs did not rise in advance
of deglaciation south of the modern California Current front. Glacial
warming along the California margin therefore is a regional signal of
the weakening of the California Current during times when large ice
sheets reorganized wind systems over the North Pacific. Both the timing
and magnitude of the SST estimates suggest that the Devils Hole
(Nevada) calcite record represents regional but not global
paleotemperatures, and hence does not pose a fundamental challenge to
the orbital ("Milankovitch") theory of the Ice Ages.
1 Department of Geological Sciences, Brown
University, Providence, RI 02912, USA.
2 University
of California, Santa Cruz, CA 95064, USA.
3 Lamont-Doherty Earth Observatory, Palisades, NY
10964, USA.
4 Center for Geophysical Investigation
of the Shallow Subsurface, Boise State University, Boise, ID 83725, USA.
5 Oregon State University, Corvallis, OR 97331, USA.
6 University of Southern California, Los
Angeles, CA 90089, USA.
7 Centro de
Investigación Científica y de Educación Superior de
Ensenada, Ensenada 22860, Mexico.
*
To whom correspondence should be addressed.
