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Climate of the Past An interactive open-access journal of the European Geosciences Union
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
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).
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 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 88 ka. 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 853 m using chemical species with seasonally-varying behaviours. The annual layer counted age at 853 m is 2332 years before 2000 (y b2k) with an error of +13/−7 y, i.e. 2345–2325 y 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 (2332 y b2k) and the age ties from ~ 2400–4000 y 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 8200 y b2k event. The improved age control between 9000 and 21000 y b2k is supplemented by CH4 and δ18O ice measurements (Pedro et al., 2011). Over the period 16600 to 18600 y 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.

Citation: Roberts, J., Moy, A., Plummer, C., van Ommen, T., Curran, M., Vance, T., Poynter, S., Liu, Y., Pedro, J., Treverrow, A., Tozer, C., Jong, L., Whitehouse, P., Loulergue, L., Chappellaz, J., Morgan, V., Spahni, R., Schilt, A., MacFarling Meure, C., Etheridge, D., and Stocker, T.: A revised Law Dome age model (LD2017) and implications for last glacial climate, Clim. Past Discuss., https://doi.org/10.5194/cp-2017-96, in review, 2017.
Jason Roberts et al.
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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