Publication Date:
2022-05-25
Description:
Author Posting. © American Geophysical Union, 2010. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 25 (2010): PA2202, doi:10.1029/2008PA001645.
Description:
Unraveling the processes responsible for Earth's climate transition from an “El Niño–like state” during the warm early Pliocene into a modern-like “La Niña–dominated state” currently challenges the scientific community. Recently, the Pliocene climate switch has been linked to oceanic thermocline shoaling at ∼3 million years ago along with Earth's final transition into a bipolar icehouse world. Here we present Pliocene proxy data and climate model results, which suggest an earlier timing of the Pliocene climate switch and a different chain of forcing mechanisms. We show that the increase in North Atlantic meridional overturning circulation between 4.8 and 4.0 million years ago, initiated by the progressive closure of the Central American Seaway, triggered overall shoaling of the tropical thermocline. This preconditioned the turnaround from a warm eastern equatorial Pacific to the modern equatorial cold tongue state about 1 million years earlier than previously assumed. Since ∼3.6–3.5 million years ago, the intensification of Northern Hemisphere glaciation resulted in a strengthening of the trade winds, thereby amplifying upwelling and biogenic productivity at low latitudes.
Description:
Funding for this research was provided by the Deutsche Forschungsgemeinschaft (DFG) through projects Ti 240/7, Ti 240/12 (being part of the DFG Research Unit, FOR 451: Impact of Gateways on Ocean Circulation, Climate, and Evolution at Kiel University), and Ti 240/17 and through the DFG Research Center/Excellence Cluster “The Ocean in the Earth System” at the University of Bremen. A. Timmermann is supported by the Japan Agency for Marine-Earth Science and Technology through its sponsorship of the International Pacific Research Center.
Keywords:
Pliocene
;
Thermohaline circulation
;
East Pacific cold tongue
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
Format:
text/plain
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