Steph, Silke; Tiedemann, Ralf; Prange, Matthias; Groeneveld, Jeroen; Schulz, Michael; Timmermann, Axel; Nuernberg, Dirk; Ruehlemann, Carsten; Saukel, Cornelia; Haug, Gerald H. (2010): Early Pliocene increase in thermohaline overturning; a precondition for the development of the modern Equatorial Pacific cold tongue. American Geophysical Union, Washington, DC, United States, Paleoceanography, 25 (2), georefid:2012-099718

Abstract:
Unraveling the processes responsible for Earth's climate transition from an "El Nino-like state" during the warm early Pliocene into a modern-like "La Nina-dominated state" currently challenges the scientific community. Recently, the Pliocene climate switch has been linked to oceanic thermocline shoaling at approximately 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 approximately 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.
Coverage:
West: -86.2700 East: -78.4422 North: 16.3313 South: -.4000
Relations:
Expedition: 165
Site: 165-1000
Site: 165-999
Expedition: 202
Site: 202-1239
Site: 202-1241
Data access:
Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=10.1029/2008PA001645 (c.f. for more detailed metadata)
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