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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 2
Clim. Past, 11, 153–173, 2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Clim. Past, 11, 153–173, 2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 05 Feb 2015

Research article | 05 Feb 2015

The WAIS Divide deep ice core WD2014 chronology – Part 1: Methane synchronization (68–31 ka BP) and the gas age–ice age difference

C. Buizert1, K. M. Cuffey2, J. P. Severinghaus3, D. Baggenstos3, T. J. Fudge4, E. J. Steig4, B. R. Markle4, M. Winstrup4, R. H. Rhodes1, E. J. Brook1, T. A. Sowers5, G. D. Clow6, H. Cheng7,8, R. L. Edwards8, M. Sigl9, J. R. McConnell9, and K. C. Taylor9 C. Buizert et al.
  • 1College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
  • 2Department of Geography, University of California, Berkeley, CA 94720, USA
  • 3Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA
  • 4Quaternary Research Center and Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
  • 5Department of Geosciences and Earth and Environmental Systems Institute, Pennsylvania State University, University Park, PA 16802, USA
  • 6US Geological Survey, Boulder, CO 80309, USA
  • 7Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, China
  • 8Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA
  • 9Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA

Abstract. The West Antarctic Ice Sheet Divide (WAIS Divide, WD) ice core is a newly drilled, high-accumulation deep ice core that provides Antarctic climate records of the past ∼68 ka at unprecedented temporal resolution. The upper 2850 m (back to 31.2 ka BP) have been dated using annual-layer counting. Here we present a chronology for the deep part of the core (67.8–31.2 ka BP), which is based on stratigraphic matching to annual-layer-counted Greenland ice cores using globally well-mixed atmospheric methane. We calculate the WD gas age–ice age difference (Δage) using a combination of firn densification modeling, ice-flow modeling, and a data set of δ15N-N2, a proxy for past firn column thickness. The largest Δage at WD occurs during the Last Glacial Maximum, and is 525 ± 120 years. Internally consistent solutions can be found only when assuming little to no influence of impurity content on densification rates, contrary to a recently proposed hypothesis. We synchronize the WD chronology to a linearly scaled version of the layer-counted Greenland Ice Core Chronology (GICC05), which brings the age of Dansgaard–Oeschger (DO) events into agreement with the U/Th absolutely dated Hulu Cave speleothem record. The small Δage at WD provides valuable opportunities to investigate the timing of atmospheric greenhouse gas variations relative to Antarctic climate, as well as the interhemispheric phasing of the "bipolar seesaw".

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