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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 11
Clim. Past, 14, 1819-1850, 2018
https://doi.org/10.5194/cp-14-1819-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Clim. Past, 14, 1819-1850, 2018
https://doi.org/10.5194/cp-14-1819-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 28 Nov 2018

Research article | 28 Nov 2018

Carbon burial in deep-sea sediment and implications for oceanic inventories of carbon and alkalinity over the last glacial cycle

Olivier Cartapanis1,2, Eric D. Galbraith1,3,4, Daniele Bianchi5, and Samuel L. Jaccard2 Olivier Cartapanis et al.
  • 1Earth and Planetary Sciences McGill University, Montreal H3A 2A7, Canada
  • 2Institute of Geological Sciences and Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
  • 3Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, 08010 Barcelona, Spain
  • 4Institut de Ciència i Tecnologia Ambientals (ICTA) and Department of Mathematics, Universitat Autònoma de Barcelona, 08193 Barcelona, Spain
  • 5Department of Atmospheric and Oceanic Sciences, University of California Los Angeles, Los Angeles, CA 90095-1565, USA

Abstract. Although it has long been assumed that the glacial–interglacial cycles of atmospheric CO2 occurred due to increased storage of CO2 in the ocean, with no change in the size of the active carbon inventory, there are signs that the geological CO2 supply rate to the active pool varied significantly. The resulting changes of the carbon inventory cannot be assessed without constraining the rate of carbon removal from the system, which largely occurs in marine sediments. The oceanic supply of alkalinity is also removed by the burial of calcium carbonate in marine sediments, which plays a major role in air–sea partitioning of the active carbon inventory. Here, we present the first global reconstruction of carbon and alkalinity burial in deep-sea sediments over the last glacial cycle. Although subject to large uncertainties, the reconstruction provides a first-order constraint on the effects of changes in deep-sea burial fluxes on global carbon and alkalinity inventories over the last glacial cycle. The results suggest that reduced burial of carbonate in the Atlantic Ocean was not entirely compensated by the increased burial in the Pacific basin during the last glacial period, which would have caused a gradual buildup of alkalinity in the ocean. We also consider the magnitude of possible changes in the larger but poorly constrained rates of burial on continental shelves, and show that these could have been significantly larger than the deep-sea burial changes. The burial-driven inventory variations are sufficiently large to have significantly altered the δ13C of the ocean–atmosphere carbon and changed the average dissolved inorganic carbon (DIC) and alkalinity concentrations of the ocean by more than 100µM, confirming that carbon burial fluxes were a dynamic, interactive component of the glacial cycles that significantly modified the size of the active carbon pool. Our results also suggest that geological sources and sinks were significantly unbalanced during the late Holocene, leading to a slow net removal flux on the order of 0.1PgCyr−1 prior to the rapid input of carbon during the industrial period.

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A data-based reconstruction of carbon-bearing deep-sea sediment shows significant changes in the global burial rate over the last glacial cycle. We calculate the impact of these deep-sea changes, as well as hypothetical changes in continental shelf burial and volcanic outgassing. Our results imply that these geological fluxes had a significant impact on ocean chemistry and the global carbon isotopic ratio, and that the natural carbon cycle was not in steady state during the Holocene.
A data-based reconstruction of carbon-bearing deep-sea sediment shows significant changes in the...
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