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Discussion papers | Copyright
https://doi.org/10.5194/cp-2017-96
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Aug 2017

Research article | 23 Aug 2017

Review status
This discussion paper is a preprint. It has been under review for the journal Climate of the Past (CP). A final paper in CP is not foreseen.

A revised Law Dome age model (LD2017) and implications for last glacial climate

Jason Roberts1,2, Andrew Moy1,2, Christopher Plummer2,3, Tas van Ommen1,2, Mark Curran1,2, Tessa Vance2, Samuel Poynter2, Yaping Liu4, Joel Pedro5, Adam Treverrow2, Carly Tozer2,6, Lenneke Jong2,3, Pippa Whitehouse7, Laetitia Loulergue8, Jerome Chappellaz8, Vin Morgan1,2, Renato Spahni9, Adrian Schilt9, Cecilia MacFarling Meure10, David Etheridge10, and Thomas Stocker9 Jason Roberts et al.
  • 1Australian Antarctic Division, Kingston, Tasmania 7050, Australia
  • 2Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania 7001, Australia
  • 3Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7001, Australia
  • 4State Key Laboratory of Cryospheric Sciences, Northwest Institute of Eco-Environment and Resources, CAS, Lanzhou, 730000, China
  • 5Center for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
  • 6Faculty of Science & Information Technology, University of Newcastle, Callaghan, New South Wales 2308, Australia
  • 7Department of Geography, Durham University, Durham, DH1 3LE, UK
  • 8University Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
  • 9Climate and Environmental Physics, Physics Institute and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
  • 10Climate Science Centre, CSIRO Oceans and Atmosphere, Aspendale Victoria 3195 Australia

Abstract. Here we present a revised Law Dome, Dome Summit South (DSS) ice core age model (denoted LD2017) that significantly improves the chronology over the last 88ka. An ensemble approach was used, allowing for the computation of both a median age and associated uncertainty as a function of depth. The revised chronology incorporates extended continuous annual layer counting to 853m using chemical species with seasonally-varying behaviours. The annual layer counted age at 853m is 2332 years before 2000 (y b2k) with an error of +13/−7y, i.e. 2345–2325y b2k . Below this depth, non-linear interpolation between age ties using a probability density function for age/depth is used to constrain and model the age of the ice. The ice-based age ties below the annual layer counted section are based on matching volcanic event markers, methane (CH4) gas concentration, isotopic composition of ice (δ18O) and the Last Glacial Maximum (LGM) dust peak to other records. For consistency, the timescale used for all matching is the AICC2012 timescale (Veres et al., 2013). The first ice-based age tie is the base of the annual layer counting record (2332y b2k) and the age ties from ~2400–4000y b2k are volcanic synchronised ice-based age ties. The detection of abrupt changes in CH4 gas concentrations within the DSS record provides further independent gas-based age ties, including the tightly constrained 8200y b2k event. The improved age control between 9000 and 21000y b2k is supplemented by CH4 and δ18O ice measurements (Pedro et al., 2011). Over the period 16600 to 18600y b2k large changes in dust concentration, matched to the EDC dust record, are used to constrain two ice-based age ties. Unlike previous studies, where the modelling was used to simultaneously infer both age and snow accumulation rate, we made an independent estimate of the snow accumulation rate, where required, for the use of gas based age ties.

Jason Roberts et al.
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Jason Roberts et al.
Jason Roberts et al.
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Here we present a revised Law Dome, Dome Summit South (DSS) ice core age model (denoted LD2017) that significantly improves the chronology over the last 88 thousand years. An ensemble approach was used, allowing for the computation of both a median age and associated uncertainty as a function of depth. We use a non-linear interpolation between age ties and unlike previous studies, we made an independent estimate of the snow accumulation rate, where required, for the use of gas based age ties.
Here we present a revised Law Dome, Dome Summit South (DSS) ice core age model (denoted LD2017)...
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