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High-latitude influence on the eastern equatorial Pacific climate in the early Pleistocene epoch

Map of Core location and modern Sea Surface Temperature High-latitude influence on the eastern equatorial Pacific climate in the early Pleistocene epoch
Nature, Vol. 427, No.6976, pp. 720 - 723, 19 February 2004.

Zhonghui Liu & Timothy D. Herbert

Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA
ABSTRACT:
Many records of tropical sea surface temperature and marine productivity exhibit cycles of 23 kyr (orbital precession) and 100 kyr during the past 0.5Myr, whereas high-latitude sea surface temperature records display much more pronounced obliquity cycles at a period of about 41 kyr. Little is known, however, about tropical climate variability before the mid-Pleistocene transition about 900 kyr ago, which marks the change from a climate dominated by 41-kyr cycles (when ice-age cycles and high-latitude sea surface temperature variations were dictated by changes in the Earth's obliquity) to the more recent 100-kyr cycles of ice ages. Here we analyse alkenones from marine sediments in the eastern equatorial Pacific Ocean to reconstruct sea surface temperatures and marine productivity over the past 1.8Myr. We find that both records are dominated by the 41-kyr obliquity cycles between 1.8 and 1.2Myr ago, with a relatively small contribution from orbital precession, and that early Pleistocene sea surface temperatures varied in the opposite sense to local annual insolation in the eastern equatorial Pacific Ocean. We conclude that during the early Pleistocene epoch, climate variability at our study site must have been determined by high-latitude processes that were driven by orbital obliquity forcing.

Download data from the WDC Paleo archive:
Eastern Pacific Pleistocene Alkenone Data and SST Reconstruction
Data also available in Microsoft Excel format.

To read or view the full study, please visit the Nature website.
It was published in Nature, Vol. 427, No.6976, pp. 720 - 723, 19 February 2004.

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8 February 2005