Gradual and abrupt changes during the Mid-Pleistocene Transition

QUATERNARY SCIENCE REVIEWS

卷:148

Article

Ford, Heather L.¹  Sosdian, Sindia M.²  Rosenthal, Yair^3,4  Raymo, Maureen E.¹ 

[1] Lamont Doherty Earth Observ, Biol & Paleo Environm, Palisades, NY 10964 USA

[2] Cardiff Univ, Sch Earth & Ocean Sci, Cardiff, S Glam, Wales

[3] Rutgers State Univ, Dept Marine & Coastal Sci, New Brunswick, NJ USA

[4] Rutgers State Univ, Dept Earth & Atmospher Sci, New Brunswick, NJ USA

关键词: Palaeoceanography;    Benthic foraminifera;    Mg/Ca;    Mid-Pleistocene Transition;   

DOI  :  10.1016/j.quascirev.2016.07.005

来源: Elsevier

【 摘 要 】

During the Mid-Pleistocene Transition (MPT), the dominant glacial-interglacial cyclicity as inferred from the marine delta O-18 records of benthic foraminifera (delta O-18(benthic)) changed from 41 kyr to 100 kyr years in the absence of a comparable change in orbital forcing. Currently, only two Mg/Ca-derived, high-resolution bottom water temperature (BWT) records exist that can be used with delta O-18(benthic) records to separate temperature and ice volume signals over the Pleistocene. However, these two BWT records suggest a different pattern of climate change occurred over the MPT-a record from North Atlantic DSDP Site 607 suggests BWT decreased with no long-term trend in ice volume over the MPT, while South Pacific ODP Site 1123 suggests that BWT has been relatively stable over the last 1.5 Myr but that there was an abrupt increase in ice volume at similar to 900 kyr. In this paper we attempt to reconcile these two views of climate change across the MPT. Specifically, we investigated the suggestion that the secular BWT trend obtained from Mg/Ca measurements on Cibicidoides wuellerstorfi and Oridorsalis umbonatus species from N. Atlantic Site 607 is biased by the possible influence of Delta[CO32-] on Mg/Ca values in these species by generating a low-resolution BWT record using Uvigerina spp., a genus whose Mg/Ca values are not thought to be influenced by Delta[CO32-]. We find a long-term BWT cooling of similar to 2-3 degrees C occurred from 1500 to similar to 500 kyr in the N. Atlantic, consistent with the previously generated C wuellerstorfi and O. umbonatus BWT record. We also find that changes in ocean circulation likely influenced delta O-18(benthio) BWT, and delta O-18(seawater) records across the MPT. N. Atlantic BWT cooling starting at similar to 1.2 Ma, presumably driven by high-latitude cooling, may have been a necessary precursor to a threshold response in climate-ice sheet behavior at similar to 900 ka. At that point, a modest increase in ice volume and thermohaline reorganization may have caused enhanced sensitivity to the 100 kyr orbital cycle. (C) 2016 Elsevier Ltd. All rights reserved.

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