Submitted on October 24, 2008
Accepted on February 9, 2009
Greatly Expanded Tropical Warm Pool and Weakened Hadley Circulation in the Early Pliocene
Chris M. Brierley 1
, Alexey V. Fedorov 1*, Zhonghui Liu 2, Timothy D. Herbert 3, Kira T. Lawrence 4, Jonathan P. LaRiviere 5
1 Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA.
2 Department of Earth Sciences, University of Hong Kong, Hong Kong, PRC.
3 Department of Geological Sciences, Brown University, Providence, RI 02912, USA.
4 Geology and Environmental Geosciences, Lafayette College, Easton, PA 18042, USA.
5 Department of Geology, Southern Illinois University, Carbondale, IL 62901, USA.; Present address: Ocean Sciences, University of California, Santa Cruz, CA 95064, USA.
* To whom correspondence should be addressed.
Alexey V. Fedorov , E-mail: alexey.fedorov{at}yale.edu
These authors contributed equally to this work.
Explaining the Pliocene warm period remains a significant challenge. Here, we reconstruct the latitudinal distribution of sea surface temperature (SST) around 4 million years ago (Ma), during the early Pliocene. We show that the meridional temperature gradient between the equator and subtropics was greatly reduced, implying a vast poleward expansion of the ocean tropical warm pool. Corroborating evidence indicates that the Pacific temperature contrast between 0 to 32°N has evolved since 4 Ma from roughly 2 to 8°C. We argue that the meridional warm pool expansion had enormous impacts on the Pliocene climate (including a slowdown of the atmospheric Hadley circulation and El Niño–like conditions in the equatorial region). Ultimately, sustaining a climate state with weak tropical SST gradients may require additional mechanisms of ocean heat uptake.
