EGU2020-12768
https://doi.org/10.5194/egusphere-egu2020-12768
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

On new developments in accelerator mass spectrometry and how they promote our understanding of global carbon cycle dynamics during the last deglaciation

Julia Gottschalk1,2, Robert F. Anderson1, David A. Hodell3, Alfredo Martinez-Garcia4, Alain Mazaud5, Elisabeth Michel5, Luke C. Skinner3, Anja Studer4, Sönke Szidat6, Lena M. Thöle2, and Samuel L. Jaccard2
Julia Gottschalk et al.
  • 1Columbia University of the City of New York, Lamont-Doherty-Earth Observatory, United States of America (jgottsch@ldeo.columbia.edu)
  • 2Institute of Geological Sciences and Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland
  • 3Godwin Laboratory for Palaeoclimate Research, Earth Sciences Department, University of Cambridge, Cambridge, UK
  • 4Max Planck Institute for Chemistry, Climate Geochemistry Department, Mainz, Germany
  • 5Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, Université de Paris-Saclay, Gif, France
  • 6Department of Chemistry and Biochemistry and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland

Ocean-atmosphere 14C disequilibria of the surface and deep ocean reflect past changes in the efficiency of ocean-atmosphere CO2 exchange and ocean mixing, while it may also be related to variations in global-ocean respired carbon content. A full assessment of the oceanic mechanisms controlling deglacial changes in atmospheric CO2 is complicated by a lack of high-resolution 14C ventilation age estimates from the Southern Ocean and other key regions due to low foraminiferal abundances in marine sediments in those areas. Here we present high-resolution deglacial 14C ventilation age records from key sites in the Atlantic and Indian Sector of the Southern Ocean obtained by radiocarbon analyses of small benthic and planktic foraminiferal samples (<1 mg CaCO3) with the UniBe Mini-Carbon Dating System (MICADAS). Our analyses specifically circumvent foraminiferal sample size requirements related to “conventional” accelerator mass spectrometer analyses involving sample graphitization (>1 mg CaCO3 in most laboratories). Complementing multi-proxy analyses of sea surface temperature (SST) changes at these sites allow the construction of a radiocarbon-independent age model through a stratigraphic alignment of SST changes to Antarctic (ice core) temperature variations. We demonstrate the value of refining the age models of our study cores on the basis of high-resolution sedimentary U- and Th flux estimates, which allows an improved quantification of surface ocean reservoir age variations in the past. The resulting deep-ocean ventilation age changes are compared against qualitative and quantitative indicators of bottom water [O2] variations, in order to assess the role of Southern Ocean overturning dynamics in respired carbon changes at our study sites. We discuss the implications of our new radiocarbon- and bottom water [O2] data for the ocean’s role in atmospheric CO2 changes throughout the last deglaciation, and evaluate down-stream effects of southern high-latitude surface ocean reservoir age anomalies.

How to cite: Gottschalk, J., Anderson, R. F., Hodell, D. A., Martinez-Garcia, A., Mazaud, A., Michel, E., Skinner, L. C., Studer, A., Szidat, S., Thöle, L. M., and Jaccard, S. L.: On new developments in accelerator mass spectrometry and how they promote our understanding of global carbon cycle dynamics during the last deglaciation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12768, https://doi.org/10.5194/egusphere-egu2020-12768, 2020.

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