09 Jan 2023
09 Jan 2023
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

The effect of Pliocene regional climate changes on silicate weathering: a potential amplifier of Pliocene-Pleistocene cooling

Pierre Maffre, John C. H. Chiang, and Nicholas L. Swanson-Hysell Pierre Maffre et al.
  • University of California, Berkeley

Abstract. The warmer early Pliocene climate featured changes to global sea surface temperature (SST) patterns, namely a reduction to the equator-pole gradient and to the east-west SST gradient in the tropical Pacific, the so-called “permanent El Niño”. Here we investigate the consequences of the SST changes to silicate weathering and thus to atmospheric CO2 on geological timescales. Different SST patterns than today imply regional modifications of the hydrological cycle that directly affects continental silicate weathering in particular over tropical “hotspots” of weathering such as the Maritime continent, thus leading to a “weatherability pattern effect”. We explore the impact of Pliocene SST changes on weathering using climate model and silicate weathering model simulations, and deduce CO2 and temperature at C cycle equilibrium between solid Earth degassing and silicate weathering. In general, we find large regional increases and decreases to weathering fluxes that largely cancel out one another. For permanent El Niño conditions, weathering decreases outweigh the increases, leading to a small amplification of warming relative to the present-day by 0.4 °C. The demise of permanent El Niño could have had a small amplifying effect on cooling from the early Pliocene into the Pleistocene. For the reduced equator-pole gradient, the weathering increases and decreases largely cancel leading to no detectable difference in global temperature at C cycle equilibrium.

Pierre Maffre et al.

Status: open (until 06 Mar 2023)

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Pierre Maffre et al.

Pierre Maffre et al.


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Short summary
CO2 consumption by chemical alteration of continental silicate rocks regulates atmospheric CO2, and Earth's mean climate. The efficiency of this regulation is affected by the amount of continental precipitation, and may have been reduced 3 to 4 million years ago because of different patterns of sea surface temperature. This process could have contributed to the warmer climate of that time.