Preprints
https://doi.org/10.5194/cp-2022-2
https://doi.org/10.5194/cp-2022-2
 
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11 Jan 2022
11 Jan 2022
Status: a revised version of this preprint was accepted for the journal CP and is expected to appear here in due course.

Stratigraphic templates for ice core records of the past 1.5 million years

Eric W. Wolff1, Hubertus Fischer2, Tas van Ommen3, and David A. Hodell1 Eric W. Wolff et al.
  • 1Dept of Earth Sciences, University of Cambridge, UK
  • 2Climate and Environmental Physics, Physics Institute & Oeschger Centre for Climate Change Research, University of Bern, Switzerland
  • 3Australian Antarctic Division and Australian Antarctic Program Partnership, University of Tasmania, Tasmania, Australia

Abstract. The international ice core community has a target to obtain continuous ice cores stretching back as far as 1.5 million years. This would provide vital data (including a CO2 profile) allowing us to assess ideas about the cause of the Mid-Pleistocene Transition (MPT). The European Beyond EPICA project and the Australian Million Year Ice Core project each plan to drill such a core in the region known as Little Dome C. Dating the cores will be challenging, and one approach will be to match some of the records obtained with existing marine sediment datasets, informed by similarities in the existing 800 kyr period. Water isotopes in Antarctica have been shown to closely mirror deepwater temperature, estimated from Mg / Ca ratios of benthic foraminifera, in a marine core on the Chatham Rise near to New Zealand. The dust record in ice cores resembles very closely a South Atlantic marine record of iron accumulation rate. By assuming these relationships continue beyond 800 ka, our ice core record could be synchronised to dated marine sediments. This could be supplemented, and allow synchronisation at higher resolution, by the identification of rapid millennial scale-events that are observed both in Antarctic methane records and in emerging records of planktic oxygen isotopes and alkenone sea surface temperature (SST) from the Portuguese Margin. Although published data remain quite sparse, it should also be possible to match 10Be from ice cores to records of geomagnetic palaeointensity and authigenic 10Be/9Be in marine sediments. However, there are a number of issues that have to be resolved before the ice core 10Be record can be used. The approach of matching records to a template will be most successful if the new core is in stratigraphic order, but should also provide constraints on disordered records, if used in combination with absolute radiogenic ages.

Eric W. Wolff et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2022-2', Anonymous Referee #1, 07 Feb 2022
  • RC2: 'Comment on cp-2022-2', Lorraine Lisiecki, 08 Mar 2022
  • RC3: 'Review of “Stratigraphic templates for ice core records of the past 1.5 million years” by Eric Wolff et al.', Anonymous Referee #3, 15 Mar 2022
  • RC4: 'Comment on cp-2022-2', Anonymous Referee #4, 22 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2022-2', Anonymous Referee #1, 07 Feb 2022
  • RC2: 'Comment on cp-2022-2', Lorraine Lisiecki, 08 Mar 2022
  • RC3: 'Review of “Stratigraphic templates for ice core records of the past 1.5 million years” by Eric Wolff et al.', Anonymous Referee #3, 15 Mar 2022
  • RC4: 'Comment on cp-2022-2', Anonymous Referee #4, 22 Mar 2022

Eric W. Wolff et al.

Eric W. Wolff et al.

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Co-editor-in-chief
Reviewer 2 of that paper made a clear statement about that paper which can be used at the present level. "This manuscript’s goal is to provide recommendations for how best to develop age models for new ice cores that are anticipated to retrieve ice from 0.8-1.5 Myr ago. As significant resources are being invested to retrieve this ice, the thoughtful advance planning for the creation of these age models is commendable. In proposing specific age modeling strategies, the manuscript also generates useful hypotheses about the types of climate responses that are expected to be found in the new ice cores."
Short summary
Projects are underway to drill ice cores in Antarctica reaching 1.5 million years back in time. dating such cores will be challenging. One method is to match records from the new core against datasets from existing marine sediment cores. Here we explore the options for doing this and assess how well the ice and marine records match over the existing 800000 year time period. We are able to recommend a strategy for using marine data to place an age scale on the new ice cores.