EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

High resolution CO2 record of the great Plio-Pleistocene glaciations using boron isotopes

Rachel Brown1, Thomas Chalk1, Paul Wilson1, Eelco Rohling1,2, and Gavin Foster1
Rachel Brown et al.
  • 1School of of Ocean and Earth Science, University of Southampton, United Kingdom of Great Britain and Northern Ireland (
  • 2Research School of Earth Sciences, The Australian National University, Canberra 2601, Australia

The intensification of Northern Hemisphere glaciation (iNHG) at 3.4-2.5 million years ago (Ma) represents the last great transition in Cenozoic climate state with the development of large scale ice sheets in the Northern Hemisphere that waxed and waned with changes in insolation. Declining atmospheric CO2 levels are widely suggested to have been the main cause of iNHG but the CO2 proxy record is too poorly resolved to provide an adequate test of this hypothesis. The boron isotope-pH proxy, in particular, has shown promise when it comes to accurately estimating past CO2 concentrations and is very good at reconstructing relative changes in CO2 on orbital timescales. Here we present a new orbitally resolved record of atmospheric CO2 (1 sample per 3 kyr) change from Integrated Ocean Drilling Program Site 999 (12.74˚N, -78.74 ˚E) spanning ~2.6–2.4 Ma based on the boron isotope (δ11B) composition of planktic foraminiferal calcite, Globingerinoides ruber (senso stricto, white).  We find that δ11B values of G. ruber show clear glacial-interglacial cycles with a magnitude that is similar to those of the Mid-Pleistocene at the same site and elsewhere.  This new high-resolution view of CO2 during the first large glacial events of the Pleistocene confirms the importance of CO2 in amplifying orbital forcing of climate and offers new insights into the mechanistic drivers of natural CO2 change. 

How to cite: Brown, R., Chalk, T., Wilson, P., Rohling, E., and Foster, G.: High resolution CO2 record of the great Plio-Pleistocene glaciations using boron isotopes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10925,, 2020