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. LaRiviere5
The Pliocene warm interval has been difficult to explain. We
reconstructed the latitudinal distribution of sea surface temperature
around 4 million years ago, during the early Pliocene. Our reconstruction
shows 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 the
equator and 32°N has evolved from
2°C 4 million years
ago to
8°C today. The meridional warm pool expansion evidently
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 sea surface temperature gradients
may require additional mechanisms of ocean heat uptake (such
as enhanced ocean vertical mixing).
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 Ocean Sciences, University of California, Santa Cruz, CA 95064, USA.
* These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail: alexey.fedorov{at}yale.edu
