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Discussion papers | Copyright
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Review article 23 Apr 2018

Review article | 23 Apr 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).

Antarctic temperature and CO2: near-synchrony yet variable phasing during the last deglaciation

Jai Chowdhry Beeman1,*, Léa Gest1,*, Frédéric Parrenin1, Dominique Raynaud1, Tyler J. Fudge2, Christo Buizert3, and Edward J. Brook3 Jai Chowdhry Beeman et al.
  • 1Univ. Grenoble Alpes, CNRS, IRD, IGE, 38000 Grenoble, France
  • 2Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
  • 3College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
  • *These authors contributed equally to this work.

Abstract. The last deglaciation, which occurred from 18,000 to 11,000 years ago, is the most recent large natural climatic variation of global extent. With accurately dated paleoclimate records, we can investigate the timings of related variables in the climate system during this major transition. Here, we use an accurate relative chronology to compare regional temperature proxy data and global atmospheric CO2 as recorded in Antarctic ice cores. We build a stack of temperature variations by averaging the records from five ice cores distributed across Antarctica, and develop a volcanic synchronization to compare it with the high-resolution, robustly dated WAIS Divide CO2 record. We assess the CO2/Antarctic temperature phase relationship using a stochastic method to accurately identify the probable timings of abrupt changes in their trends. During the large, millenial-scale changes at the onset of the last deglaciation at 18ka and the onset of the Holocene at 11.5ka, Antarctic temperature most likely led CO2 by several centuries. A marked event in both series around 16ka began with a rapid rise in CO2, which stabilized synchronously with temperature. CO2 and Antarctic temperature peaked nearly synchronously at 14.4ka, the onset of the Antarctic Cold Reversal (ACR) period. And CO2 likely led Antarctic temperature by around 250 years at the end of the ACR. The five major changes identified for both series are coherent, and synchrony is within the 2σ uncertainty range for all of the changes except the Holocene onset. But the often-multimodal timings, centennial-scale substructures, and likely-variable phasings we identify testify to the complex nature of the two series, and of the mechanisms driving the carbon cycle and Antarctic temperature during the deglaciation.

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Jai Chowdhry Beeman et al.
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Jai Chowdhry Beeman et al.
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LinearFit 2.0 (plus CO2 and ATS2 Time Series Data) J. Chowdhry Beeman, F. Parrenin, and L. Gest

Jai Chowdhry Beeman et al.
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Short summary
Atmospheric CO2 was likely an important amplifier of global-scale, orbitally-driven warming during the last deglaciation. However, the mechanisms responsible for the rise in CO2, and the coherent rise in the Antarctic isotopic temperature record, are under debate. We use a stochastic method to identify the probable timings of abrupt changes in trends for the two records. The timings suggest complex, if likely coherent, mechanisms of coupling.
Atmospheric CO2 was likely an important amplifier of global-scale, orbitally-driven warming...