19 Jan 2023
 | 19 Jan 2023
Status: this preprint is currently under review for the journal TC.

Quantifying the Uncertainty in the Eurasian Ice-Sheet Geometry at the Penultimate Glacial Maximum (Marine Isotope Stage 6)

Oliver G. Pollard, Natasha L. M. Barlow, Lauren Gregoire, Natalya Gomez, Víctor Cartelle, Jeremy C. Ely, and Lachlan C. Astfalck

Abstract. North Sea Last Interglacial sea level is sensitive to the fingerprint of mass loss from polar ice sheets. However, the signal is complicated by the influence of glacial isostatic adjustment driven by the Penultimate Glacial Period Eurasian ice sheet and its geometry remain significantly uncertain. Here, we produce new reconstructions of the Eurasian ice sheet during the Penultimate Glacial Maximum (PGM), for use as input to sea-level and climate models, by employing large ensemble experiments from a simple ice-sheet model that depends solely on basal sheer stress, ice extent, and topography. To explore the range of uncertainty in possible ice geometries, we use a parameterised shear-stress map as input that has been developed to incorporate bedrock characteristics and ice-sheet basal processes. We perform Bayesian uncertainty quantification to calibrate against global ice-sheet reconstructions of the last deglaciation to rule out combinations of input parameters that produce unrealistic ice sheets. The refined parameter space is then applied to the PGM to create an ensemble of plausible 3D Eurasian ice-sheet geometries. Our reconstructed PGM Eurasian ice-sheet volume is 51.16±6.13 m sea-level equivalent which suggests a 14.3 % reduction in the volume of the PGM Laurentide ice-sheet. We find that the Barents-Kara Sea region displays both the largest mean volume and relative variability of 26.80 ± 3.58 m SLE while the British-Irish sector’s volume of 1.77 ± 0.11 m SLE is smallest, yet most implausible. Our new workflow may be applied to other locations and periods where ice-sheet histories have limited empirical data.

Oliver G. Pollard et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Review of the paper by Pollard et al.', Evan Gowan, 09 Feb 2023
  • RC2: 'Comment on tc-2023-5', Lev Tarasov, 24 Apr 2023

Oliver G. Pollard et al.

Oliver G. Pollard et al.


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Short summary
We use advanced statistical techniques and a simple ice-sheet model to produce an ensemble of plausible 3D shapes of the ice sheet that once stretched across northern Europe during the previous glacial maximum (140,000 years ago). This new reconstruction, equivalent in volume to 51.16 m of global mean sea-level rise, will improve the interpretation the high sea levels recorded from the Last Interglacial period (120,000 years ago) that provide a useful perspective on the future.