Modelling the Antarctic Ice Sheet across the mid-Pleistocene transition – implications for Oldest Ice

Johannes Sutter,Nanna B Karlsson,Olaf Eisen,Thomas Kleiner,Hubertus Fischer,Brice Van Liefferinge,Klaus Grosfeld

doi:10.5194/tc-13-2023-2019

Abstract

Abstract. The international endeavour to retrieve a continuous ice core, which spans the middle Pleistocene climate transition ca. 1.2–0.9 Myr ago, encompasses a multitude of field and model-based pre-site surveys. We expand on the current efforts to locate a suitable drilling site for the oldest Antarctic ice core by means of 3-D continental ice-sheet modelling. To this end, we present an ensemble of ice-sheet simulations spanning the last 2 Myr, employing transient boundary conditions derived from climate modelling and climate proxy records. We discuss the imprint of changing climate conditions, sea level and geothermal heat flux on the ice thickness, and basal conditions around previously identified sites with continuous records of old ice. Our modelling results show a range of configurational ice-sheet changes across the middle Pleistocene transition, suggesting a potential shift of the West Antarctic Ice Sheet to a marine-based configuration. Despite the middle Pleistocene climate reorganisation and associated ice-dynamic changes, we identify several regions conducive to conditions maintaining 1.5 Myr (million years) old ice, particularly around Dome Fuji, Dome C and Ridge B, which is in agreement with previous studies. This finding strengthens the notion that continuous records with such old ice do exist in previously identified regions, while we are also providing a dynamic continental ice-sheet context.

Highlights

The middle Pleistocene transition (MPT) is characterised by a shift from obliquity-driven climate cycles ( ∼ 41 000 years, 41 kyr) to the signature sawtooth ∼ 100 kyr cycles typical for the late Pleistocene
We do not find a major reorganisation of the East Antarctic Ice Sheet (EAIS) grounding line across the MPT, which is in contrast to the theory that the EAIS transitioned from a mostly land based ice sheet to a marine configuration in this interval (Raymo et al, 2006)
While we do not simulate a transition to a marine-based EAIS in the Wilkes and Aurora basins, such a process would certainly imprint on ice flow around Little Dome C” (LDC) due to proximity alone

Summary

Introduction

The middle Pleistocene transition (MPT) is characterised by a shift from obliquity-driven climate cycles ( ∼ 41 000 years, 41 kyr) to the signature sawtooth ∼ 100 kyr cycles typical for the late Pleistocene. Several theories have been put forth, striving to explain the enigmatic MPT (Raymo and Huybers, 2008). They include a shift in subglacial conditions underneath the Laurentide Ice Sheet (regolith hypothesis by Clark and Pollard, 1998), the inception of a large North American Ice Sheet (Bintanja and van de Wal, 2008) or marine East Antarctic Ice Sheet by Raymo et al (2006), ice bedrock climate feedbacks (Abe-Ouchi et al, 2013), the buildup of large ice sheets between MIS24 and 22 identified by Elderfield et al (2012), or the combination of changes in ice-sheet dynamics and the carbon cycle (Chalk et al, 2017). An expansion of the currently longest ice core record from the EPICA Dome C project (Jouzel et al, 2007) to and beyond the MPT

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Conclusion