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Science 17 July 2009:
Vol. 325. no. 5938, pp. 306 - 310
DOI: 10.1126/science.1169938
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Reports

Deep-Sea Temperature and Ice Volume Changes Across the Pliocene-Pleistocene Climate Transitions

Sindia Sosdian*,{dagger} and Yair Rosenthal

Earth has undergone profound changes since the late Pliocene, which led to the development [~2.7 million years ago (Ma)] and intensification (~0.9 Ma) of large-scale Northern Hemisphere ice sheets, recorded as transitions in the benthic foraminiferal oxygen isotope ({delta}18Ob) record. Here we present an orbitally resolved record of deep ocean temperature derived from benthic foraminiferal magnesium/calcium ratios from the North Atlantic, which shows that temperature variations are a substantial portion of the global {delta}18Ob signal. The record shows two distinct cooling events associated with the late Pliocene (LPT, 2.5 to 3 Ma) and mid-Pleistocene (MPT, 1.2 to 0.85 Ma) climate transitions. Whereas the LPT increase in ice volume is attributed directly to global cooling, the shift to 100,000-year cycles at the MPT is more likely to be a response to an additional change in ice-sheet dynamics.

Institute of Marine and Coastal Science and Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08901, USA.

{dagger} Present address: Research School of Earth Sciences, Australian National University, Canberra, ACT, 0200, Australia.

* To whom correspondence should be addressed. E-mail: sindia.sosdian{at}anu.edu.au

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