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Originally published in Science Express on 22 June 2006
Science 28 July 2006:
Vol. 313. no. 5786, pp. 492 - 495
DOI: 10.1126/science.1123296
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Research Articles

Plio-Pleistocene Ice Volume, Antarctic Climate, and the Global {delta}18O Record

M. E. Raymo,1* L. E. Lisiecki,1 Kerim H. Nisancioglu2

We propose that from ~3 to 1 million years ago, ice volume changes occurred in both the Northern and Southern Hemispheres, each controlled by local summer insolation. Because Earth's orbital precession is out of phase between hemispheres, 23,000-year changes in ice volume in each hemisphere cancel out in globally integrated proxies such as ocean {delta}18O or sea level, leaving the in-phase obliquity (41,000 years) component of insolation to dominate those records. Only a modest ice mass change in Antarctica is required to effectively cancel out a much larger northern ice volume signal. At the mid-Pleistocene transition, we propose that marine-based ice sheet margins replaced terrestrial ice margins around the perimeter of East Antarctica, resulting in a shift to in-phase behavior of northern and southern ice sheets as well as the strengthening of 23,000-year cyclicity in the marine {delta}18O record.

1 Department of Earth Science, Boston University, 685 Commonwealth Avenue, Boston, MA 02215, USA.
2 Palaeoclimates, Bjerknes Center for Climate Research, Allegaten 55, Bergen 5007, Norway.

* To whom correspondence should be addressed. E-mail: raymo{at}bu.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)