07 Nov 2022
07 Nov 2022
Status: this preprint is currently under review for the journal CP.

The ST22 chronology for the Skytrain Ice Rise ice core – part 2: an age model to the last interglacial and disturbed deep stratigraphy

Robert Mulvaney1, Eric William Wolff2, Mackenzie Grieman2,3, Helene Hoffmann2, Jack Humby1, Christoph Nehrbass-Ahles2, Rachael Rhodes2, Isobel Rowell2, Frédéric Parrenin4, Loïc Schmidely5, Hubertus Fischer5, Thomas Stocker5, Marcus Christl6, Raimund Muscheler7, Amaelle Landais8, and Frédéric Prié8 Robert Mulvaney et al.
  • 1British Antarctic Survey, Cambridge, UK
  • 2Department of Earth Sciences, University of Cambridge, UK
  • 3Reed College, Portland, Oregon, USA
  • 4Université Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
  • 5Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, Switzerland
  • 6Laboratory for Ion Beam Physics, ETH Zurich, 8093 Zurich, Switzerland
  • 7Department of Geology, Quaternary Sciences, Lund University, Sölvegatan 12, SE-22362 Lund, Sweden
  • 8Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France

Abstract. We present an age model for the 651 m deep Skytrain Ice Rise ice core. The top 2000 years have previously been dated using age markers interpolated through annual layer counting. Below this, we align the Skytrain core to the AICC2012 age model using tie points in the ice and air phase, and apply the Paleochrono program to obtain the best fit to the tie points and glaciological constraints. In the gas phase, ties are made using methane and, in critical sections, δ18Oair; in the ice phase ties are through 10Be across the Laschamps Event, and through ice chemistry related to long-range dust transport and deposition. This strategy provides a good outcome to about 108 ka (~605 m). Beyond that there are signs of flow disturbance, with a section of ice probably repeated. Nonetheless values of CH4 and δ18Oair confirm that part of the last interglacial (LIG), from about 117–126 ka (617–628 m), is present and in chronological order. Below this there are clear signs of stratigraphic disturbance, with rapid oscillation of values in both the ice and gas phase at the base of the LIG section. Based on methane values, the warmest part of the LIG and the coldest part of the penultimate glacial are missing from our record. Ice below 631 m appears to be of age >150 ka.

Robert Mulvaney et al.

Status: open (until 04 Jan 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review Mulvaney et al ST22', Anonymous Referee #1, 23 Nov 2022 reply

Robert Mulvaney et al.

Robert Mulvaney et al.


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Short summary
We present an age scale for a new ice core drilled at Skytrain Ice Rise, an ice rise facing the Ronne Ice Shelf in Antarctica. Various measurements in the ice and air phases are used to match the ice core to other Antarctic cores that have already been dated. The 651 m ice core includes ice that is confidently dated to the last interglacial, 126,000 years ago. Older ice is found deeper down, but there are flow disturbances in the deeper ice.