GC10-Pliocene-35, updated on 10 Jan 2024
The warm Pliocene: Bridging the geological data and modelling communities
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Climate and carbon cycling across the mid-Pliocene Warm Period

Deborah Tangunan1, Ian Hall1, Luc Beaufort2, Paul Halloran3, Aidan Starr1, and Alexandra Nederbragt1
Deborah Tangunan et al.
  • 1Cardiff University, School of Earth and Environmental Sciences, Cardiff, United Kingdom of Great Britain – England, Scotland, Wales (tangunand@cardiff.ac.uk)
  • 2Aix-Marseille Université, CNRS, IRD, Coll France, INRAE, CEREGE, Aix-en-Provence, France
  • 3College of Life and Environmental Sciences, University of Exeter, Exeter, UK

The mid-Piacenzian or mid-Pliocene Warm Period (mPWP; 3.264-3.025Ma) is the most recent period of sustained global warmth, which stands in contrast to the more variable and progressively cooler Pleistocene glacial-interglacial climate which followed. Global temperatures were 3˚C higher than the pre-industrial level, with atmospheric carbon dioxide (pCO2) reaching up to 410ppmv, making the mPWP the nearest past analogue for future warm climate. Thus, proxy reconstructions that can accurately capture biological response to past and projected pCO2 are crucial in understanding future climate scenarios.

Here we present initial high-resolution climatic variability and carbon cycling records from oxygen and carbon isotopes, assemblage, and morphometry of coccoliths – calcium carbonate exoskeletons produced by marine phytoplankton coccolithophores – from sediments collected during the IODP Expedition 361 at the Mozambique Channel (U1476; 15°49.25′S, 41°46.12′E; 2166m water depth), spanning 2.96 and 3.40Ma at 0.5 to 3.7kyr resolution. Previous studies show that the modern surface waters above Site U1476 are in air-sea exchange CO2 equilibrium, making Site U1476 an ideal location for pCO2 reconstructions. We also explore the expressions of coccolith isotopic vital effects from size-separated fractions that have been linked to cell size, growth rate, and calcification degree, providing empirical correlation with aqueous CO2 concentrationsand ultimately, with pCO2 levels.

Preliminary results show strong precession-related 23-kyr cyclicities prior to M2 glaciation. These cycles are associated with negative coccolith fraction δ18O (δ18OCF) excursions coinciding with increasing upper ocean primary productivity resulting from a more vigorous Mozambique Channel Throughflow, forced by precession minima and northern hemisphere summer insolation maxima. A change in orbital configuration in upper ocean temperature and stratification records, from precession to obliquity, occurs after M2, with an overall climate background of 100-kyr glacial-interglacial cycles in upper ocean primary production, indicating commencement of the longer-term 100-kyr cooling trend observed through the Pleistocene. Periodicities at the eccentricity band, often linked to Pliocene ice volume, are shown in the δ13CCF, supporting prior findings on tight coupling between ice volume and carbon cycle changes, analogous to those recorded during the late Pleistocene.

How to cite: Tangunan, D., Hall, I., Beaufort, L., Halloran, P., Starr, A., and Nederbragt, A.: Climate and carbon cycling across the mid-Pliocene Warm Period, The warm Pliocene: Bridging the geological data and modelling communities, Leeds, United Kingdom, 23–26 Aug 2022, GC10-Pliocene-35, https://doi.org/10.5194/egusphere-gc10-pliocene-35, 2022.