Reconciling ice core CO2 and land-use change following New World-Old World contact.
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Ice core records of carbon dioxide (CO2) throughout the last 2000 years provide context for the unprecedented anthropogenic rise in atmospheric CO2 and insights into global carbon cycle dynamics. Yet the atmospheric history of CO2 remains uncertain in some time intervals. Here we present measurements of CO2 and methane (CH4) in the Skytrain ice core from 1450 to 1700 CE. Results suggest a sudden decrease in CO2 around 1610 CE in one widely used record may be an artefact of a small number of anomalously low values. Our analysis supports a more gradual decrease in CO2 of 0.5 ppm per decade from 1516 to 1670 CE, with an inferred land carbon sink of 2.6 PgC per decade. This corroborates modelled scenarios of large-scale reorganisation of land use in the Americas following New World-Old World contact, whereas a rapid decrease in CO2 at 1610 CE is incompatible with even the most extreme land-use change scenarios.
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Acknowledgements: This work was primarily funded by an Antarctic Science International Bursary held by A.C.F.K. and additionally supported by Royal Society Grants URF\R1\180366 and RGF\EA\181047 held by T.K.B. and an Isaac Newton Trust award to R.H.R. The collection of the Skytrain Ice Rise core was funded by the European Research Council under the Horizon 2020 research and innovation programme (grant agreement No 742224, WACSWAIN) held by E.W.W. This material reflects only the authors’ views, and the Commission is not liable for any use that may be made of the information contained therein. E.W.W. was also supported by a Royal Society Professorship. We thank Diana Vladimirova for assistance with processing of the CH4 data, and the British Antarctic Survey CFA team for assistance in measurement of the Skytrain ice core for continuous CH4.
Funder: Antarctic Science International Bursary https://www.antarcticsciencebursary.org.uk/
Funder: Isaac Newton Trust; doi: https://doi.org/10.13039/501100004815
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2041-1723
