Preprints
https://doi.org/10.5194/cp-2021-116
https://doi.org/10.5194/cp-2021-116

  31 Aug 2021

31 Aug 2021

Review status: this preprint is currently under review for the journal CP.

An improved and continuous synchronization of the Greenland ice-core and Hulu Cave U-Th timescales using probabilistic inversion

Francesco Muschitiello1,2 Francesco Muschitiello
  • 1Department of Geography, University of Cambridge, Cambridge CB2 3EN, UK
  • 2NORCE Norwegian Research Centre, Jahnebakken 5, 5007 Bergen, Norway

Abstract. This study presents the first continuously measured transfer functions that quantify the age difference between the Greenland Ice-Core Chronology 2005 (GICC05) and the Hulu Cave U-Th timescale during the last glacial period. The transfer functions were estimated using an automated algorithm for Bayesian inversion that allows inferring a continuous and objective synchronization between Greenland ice-core and Hulu Cave proxy signals. The algorithm explicitly considers prior knowledge on the maximum counting error (MCE) of GICC05, but also samples synchronization scenarios that exceed the differential dating uncertainty of the annual-layer count in ice cores, which are currently not detectable using conventional tie-point alignments or wiggle-matching techniques. The consistency and accuracy of the results were ensured by estimating two independent synchronizations: a climate synchronization based on climate proxy records, and a climate-independent synchronization based on cosmogenic radionuclide data (i.e. 10Be and 14C). The transfer functions are up to 40 % more precise than previous estimates and significantly reduce the absolute dating uncertainty of the GICC05 back to 48 kyr ago. The results highlight that the annual-layer counting error of GICC05 is not strictly correlated over extended periods of time, and that within certain Greenland Stadials the differential dating uncertainty is likely underestimated by 7.5–20 %. Importantly, the analysis implies for the first time that during the Last Glacial Maximum GICC05 overcounts ice layers by 15–25 % –a bias attributable to a higher frequency of sub-annual layers due to changes in the seasonal cycle of precipitation and mode of dust deposition to the Greenland Ice Sheet. The new timescale transfer functions provide important constraints on the uncertainty surrounding the stratigraphic dating of the Greenland age-scale and enable an improved chronological integration of ice cores, U-Th-dated and radiocarbon-dated paleoclimate records on a common timeline. The transfer functions are available as supplements to this study.

Francesco Muschitiello

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-116', Frédéric Parrenin, 02 Oct 2021
  • RC2: 'Comment on cp-2021-116', Florian Adolphi, 05 Oct 2021
  • EC1: 'Comment on cp-2021-116', Denis-Didier Rousseau, 31 Oct 2021
  • RC3: 'Comment on cp-2021-116', Anonymous Referee #3, 01 Nov 2021

Francesco Muschitiello

Francesco Muschitiello

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Short summary
The first continuously measured transfer functions that quantify the age difference between the Greenland Ice-Core Chronology 2005 (GICC05) and the U-Th timescale are presented. The transfer functions were generated using a novel probabilistic algorithm for the synchronization of proxy signals. The results greatly improve the accuracy and precision of previous synchronization estimates and reveal that the annual-layer counting error of GICC05 is less systematic than previously assumed.