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Title: Simulating Pliocene warmth and a permanent El Niño-like state: The role of cloud albedo

Journal Article · · Paleoceanography
DOI:https://doi.org/10.1002/2014PA002644· OSTI ID:1454704
 [1];  [1]
  1. Yale Univ., New Haven, CT (United States). Department of Geology and Geophysics
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We present that available evidence suggests that during the early Pliocene (4–5 Ma) the mean east-west sea surface temperature (SST) gradient in the equatorial Pacific Ocean was significantly smaller than today, possibly reaching only 1–2°C. The meridional SST gradients were also substantially weaker, implying an expanded ocean warm pool in low latitudes. Subsequent global cooling led to the establishment of the stronger, modern temperature gradients. Given our understanding of the physical processes that maintain the present-day cold tongue in the east, warm pool in the west and hence sharp temperature contrasts, determining the key factors that maintained early Pliocene climate still presents a challenge for climate theories and models. This study demonstrates how different cloud properties could provide a solution. We show that a reduction in the meridional gradient in cloud albedo can sustain reduced meridional and zonal SST gradients, an expanded warm pool and warmer thermal stratification in the ocean, and weaker Hadley and Walker circulations in the atmosphere. Having conducted a range of hypothetical modified cloud albedo experiments, we arrive at our Pliocene simulation, which shows good agreement with proxy SST data from major equatorial and coastal upwelling regions, the tropical warm pool, middle and high latitudes, and available subsurface temperature data. As suggested by the observations, the simulated Pliocene-like climate sustains a robust El Niño-Southern Oscillation despite the reduced mean east-west SST gradient. In conclusion, our results demonstrate that cloud albedo changes may be a critical element of Pliocene climate and that simulating the meridional SST gradient correctly is central to replicating the geographical patterns of Pliocene warmth.

Research Organization:
Yale Univ., New Haven, CT (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
SC0007037
OSTI ID:
1454704
Journal Information:
Paleoceanography, Vol. 29, Issue 10; ISSN 0883-8305
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 38 works
Citation information provided by
Web of Science

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Cited By (14)

The evolution of the equatorial thermocline and the early Pliocene El Padre mean state: EL PADRE EQUATORIAL THERMOCLINE journal June 2015
On the mechanisms of warming the mid-Pliocene and the inference of a hierarchy of climate sensitivities with relevance to the understanding of climate futures posted_content March 2018
Monsoon Responses to Climate Changes—Connecting Past, Present and Future journal March 2019
Tightly linked zonal and meridional sea surface temperature gradients over the past five million years journal November 2015
Late Miocene climate cooling and intensification of southeast Asian winter monsoon journal April 2018
The seesaw response of the intertropical and South Pacific convergence zones to hemispherically asymmetric thermal forcing journal December 2019
The seesaw response of the Intertropical and South Pacific convergence zones to hemispherically asymmetric thermal forcing journal May 2020
Modeling a modern-like pCO2 warm period (Marine Isotope Stage KM5c) with two versions of an Institut Pierre Simon Laplace atmosphere–ocean coupled general circulation model journal January 2020
Drought Indices, Drought Impacts, CO2, and Warming: a Historical and Geologic Perspective journal April 2018
The seesaw response of the Intertropical and South Pacific convergence zones to hemispherically asymmetric thermal forcing journal April 2021
On the mechanisms of warming the mid-Pliocene and the inference of a hierarchy of climate sensitivities with relevance to the understanding of climate futures journal January 2018
Estimates of Pliocene Tropical Pacific Temperature Sensitivity to Radiative Greenhouse Gas Forcing journal January 2019
Reductions in Strong Upwelling‐Favorable Wind Events in the Pliocene journal December 2019
Multiproxy Reduced‐Dimension Reconstruction of Pliocene Equatorial Pacific Sea Surface Temperatures journal January 2020

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Related Subjects

58 GEOSCIENCES
Pliocene climate
cloud albedo