Exceptionally high biosphere productivity at the beginning of Marine Isotopic Stage 11

Margaux Brandon,Amaelle Landais,Violaine Favre,Héloïse Abrial,Thomas Extier,Léa Schmitz,Stéphanie Duchamp-Alphonse,Thomas Blunier,Frédéric Prié

doi:10.1038/s41467-020-15739-2

Abstract

Significant changes in atmospheric CO2 over glacial-interglacial cycles have mainly been attributed to the Southern Ocean through physical and biological processes. However, little is known about the contribution of global biosphere productivity, associated with important CO2 fluxes. Here we present the first high resolution record of Δ17O of O2 in the Antarctic EPICA Dome C ice core over Termination V and Marine Isotopic Stage (MIS) 11 and reconstruct the global oxygen biosphere productivity over the last 445 ka. Our data show that compared to the younger terminations, biosphere productivity at the end of Termination V is 10 to 30 % higher. Comparisons with local palaeo observations suggest that strong terrestrial productivity in a context of low eccentricity might explain this pattern. We propose that higher biosphere productivity could have maintained low atmospheric CO2 at the beginning of MIS 11, thus highlighting its control on the global climate during Termination V.

Highlights

Significant changes in atmospheric CO2 over glacial-interglacial cycles have mainly been attributed to the Southern Ocean through physical and biological processes
Some information on carbon stocks can be obtained from δ13C of carbonates using a wealth of data obtained from marine sediments[10] and δ13C of atmospheric CO211,12
To check the coherency between the previous records that did not take into account these corrections, and the new one obtained on EPICA Dome C (EDC), we measured Δ17O of O2 over Termination II on the EDC ice core and compared our corrected Δ17O of O2 curve with the previous record obtained by Blunier et al.[22] on the Vostok ice core (Fig. 1)

Summary

Introduction

Significant changes in atmospheric CO2 over glacial-interglacial cycles have mainly been attributed to the Southern Ocean through physical and biological processes. Quantifying changes in the carbon cycle over deglaciations relies on data compilation and modelling studies to estimate both carbon stocks and carbon fluxes[8]. Past changes in biological carbon pump are best represented by changes in buried organic biomarkers combined with marine Total Organic Carbon/Particulate Inorganic Carbon ratio (TOC/CaCO3), suggested to reflect the C-rain ratio[13]. Despite their accuracy to provide biological export production, only one site combine such records in the Southern Ocean, for the last 800 ka, so far[14]. This proxy is a complex tracer being influenced by hydrological cycle at first order[17,18] and its use as a quantitative tool for productivity reconstruction depends on the exact determination of associated fractionation factors in the water and biosphere cycles[19]

Methods

Results

Conclusion