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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Preprints
https://doi.org/10.5194/cp-2019-127
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2019-127
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

  25 Oct 2019

25 Oct 2019

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This preprint is currently under review for the journal CP.

Plateaus and jumps in the atmospheric radiocarbon record – Potential origin and value as global age markers for glacial-to-deglacial paleoceanography, a synthesis

Michael Sarnthein1, Kevin Küssner2, Pieter M. Grootes3, Blanca Ausin4, Timothy Eglinton4, Juan Muglia5, Raimund Muscheler6, and Gordon Schlolaut7 Michael Sarnthein et al.
  • 1Institute of Geosciences, University of Kiel, Olshausenstr. 40, 24098 Kiel, Germany
  • 2Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung, Department for Marine Geology, 27570 Bremerhaven, Germany
  • 3Institute of Ecosystem Research, University of Kiel, Olshausenstr. 40, 24098 Kiel, Germany
  • 4Geological Institute, ETH Zürich, Sonneggstr. 5, 8092 Zuerich, Switzerland
  • 5College of Earth, Ocean and Atmospheric Sciences, Oregon State University, 104, CEOAS Administration Building, 101 SW 26th St, Corvallis, OR 97331, USA
  • 6Quaternary Sciences, Department of Geology Lund University, Sölvegatan 12, S-223 62 Lund, Sweden
  • 7Climate Dynamics and Landscape Evolution,GFZ German Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany

Abstract. Changes in the geometry of ocean Meridional Overturning Circulation (MOC) are crucial in controlling changes of climate and the carbon inventory of the atmosphere. However, the precise timing and global correlation of short-term glacial-to-deglacial changes of MOC in different ocean basins still present a major challenge. A possible solution is offered by the fine structure of jumps and plateaus in the record of radio-carbon (14C) concentration of the atmosphere and surface ocean that reflects changes in atmospheric 14C production as well as in the 14C exchange between air and sea and within the ocean. Boundaries of atmospheric 14C plateaus in the 14C record of Lake Suigetsu, now tied to Hulu U/Th model-ages instead of optical varve counts, provide a stratigraphic "rung ladder" of ~30 age tie points from 29 to 10 ka for correlation with and dating of planktic oceanic 14C records. The age difference between contemporary planktic and atmospheric 14C plateaus gives an estimate of the global distribution of 14C reservoir ages for surface waters of the Last Glacial Maximum (LGM) and deglacial Heinrich Stadial 1 (HS-1), as shown by 19 planktic 14C records. Clearly elevated and variable reservoir ages mark both high-latitude sites covered by sea ice and/or meltwater and upwelling regions. 14C ventilation ages of LGM deep waters reveal opposed geometries of Atlantic and Pacific MOC. Similar to today, Atlantic deep-water formation went along with an estuarine inflow of old abyssal waters from the Southern Ocean up to the northern North Pacific and an outflow of upper deep waters. Vice versa, 14C ventilation ages suggest a reversed MOC during early HS-1 and a ~1500 year long flushing of the deep North Pacific up to the South China Sea, when estuarine circulation geometry marked the North Atlantic, gradually starting near 19 ka. Elevated 14C ventilation ages of LGM deep waters reflect a major drawdown of carbon from the atmosphere. Inversely, the subsequent massive age drop and change in MOC induced two major events of carbon release to the atmosphere as recorded in Antarctic ice cores, shifts that highlight the significance of ocean MOC for atmospheric CO2 and its 14C inventory. These new features of MOC and the carbon cycle offer a challenge to model simulations that, in part because of insufficient spatial model resolution and reference data for testing the model results, still poorly reproduce them.

Michael Sarnthein et al.

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Michael Sarnthein et al.

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Short summary
The dating technique of 14C-plateau tuning uses U/Th-based model ages, refinements of the Lake Suigetsu age scale, and the link of surface ocean carbon to the globally mixed atmosphere as basis of age correlation. Our synthesis employs data of 20 sediment cores from the global ocean and offers a coherent picture of global ocean circulation evolving over glacial-to-deglacial times on semi-millennial scales to be compared with climate records stored in marine sediments, ice cores, and speleothems.
The dating technique of 14C-plateau tuning uses U/Th-based model ages, refinements of the Lake...
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