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Early Pleistocene sea-surface temperature trends : early cooling, glacial intensification, and implications for the mid-Pleistocene climate transition.

McClymont, E.L. and Sosdian, S.M. and Rosell-Meléc, A. and Rosenthal, Y. (2013) 'Early Pleistocene sea-surface temperature trends : early cooling, glacial intensification, and implications for the mid-Pleistocene climate transition.', Earth-science reviews., 123 . pp. 173-193.

Abstract

The mid-Pleistocene climate transition (MPT) is defined by the emergence of high amplitude, quasi-100 ka glacial-interglacial cycles from a prior regime of more subtle 41 ka cycles. This change in periodicity and amplitude cannot be explained by a change in ‘external’ astronomical forcing. Here, we review and integrate published records of sea-surface temperatures (SSTs) to assess whether a common global expression of the MPT in the surface ocean can be recognized, and examine our findings in light of mechanisms proposed to explain climate system reorganization across the MPT. We show that glacial-interglacial variability in SSTs is superimposed upon a longer-term cooling trend in oceanographic systems spanning the low- to high-latitudes. Regional variability exists in the timing of the onset and magnitude of cooling but, in most cases, a long-term cooling trend begins or intensifies from ~1.2 Ma (Marine Isotope Stage, MIS, 35-34). The SST cooling accompanies a long-term trend towards higher global ice volume as recorded in benthic foraminifera d18O, but pre-dates a step-like increase in d18O at ~0.9 Ma (MIS 24-22) that is argued to reflect expansion of continental ice-sheets. The strongest expression of Pleistocene cooling is found during glacial stages, whereas minor or negligible trends in interglacial temperatures are identified. However, pronounced cooling during both glacial and interglacial maxima is evident at 0.9 Ma. Alongside the long-term SST cooling trends, quasi-100 ka cycles begin to emerge in both the SST and d18O records at 1.2 Ma, and become dominant with the expansion of the ice-sheets at 0.9 Ma. We show that the intensified glacial-stage cooling is accompanied by evolving pCO2, abyssal ocean ventilation, atmospheric circulation and/or dust inputs to the Southern Ocean. These changes in diverse environmental parameters suggest that glacial climate boundary conditions evolved across the MPT. In turn, these modified boundary conditions may have altered climate sensitivity to orbital forcing by placing pre-existing ice-sheets closer to some threshold of climate-ice sheet response.

Item Type:Article
Keywords:Sea surface temperatures, Mid-Pleistocene transition, Ice sheets, 100 kyr world.
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1016/j.earscirev.2013.04.006
Publisher statement:NOTICE: this is the author’s version of a work that was accepted for publication in Earth-science reviews. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Earth-science reviews. 123, 2013, 10.1016/j.earscirev.2013.04.006
Date accepted:No date available
Date deposited:17 May 2013
Date of first online publication:August 2013
Date first made open access:No date available

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