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

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.

Multi-tracer study of gas trapping in an East Antarctic ice core

“…Indeed, ice cores have the unparalleled characteristic of containing various past climatic information in the ice matrix and the air bubbles within (e.g., Petit et al, 1999;Jouzel et al, 2007;Brook and Buizert, 2018). In particular, the bubbles enclosed in polar ice contain air that dates back to their time of formation, and their analysis can be used to reconstruct the atmospheric composition history over more than 800 kyr (Stauffer et al, 1985;Loulergue et al, 2008;Lüthi et al, 2008;Bereiter et al, 2014;Tison et al, 2015). The bubbles become progressively formed in the ice at depths approximately ranging from 50 to 120 m below the surface of the ice sheet, depending on the local temperature and accumulation conditions.…”

Exploring the impact of atmospheric forcing and basal boundary conditions on the simulation of the Antarctic ice sheet at the Last Glacial Maximum

“…CC BY 4.0 License. et al, 2014;Sutter et al, 2019). Nevertheless we have shown here that the spread of the simulated ice volume and ice extension for different climatic outputs can be equal to or larger than that resulting from different basal-dragging choices.…”

“…Whereas older studies estimated large sea-level contributions generally above 15 m (e.g. Nakada et al (2000); Huybrechts (2002); Peltier and Fairbanks (2006); Philippon et al (2006); Bassett et al (2007)), more recent modelling studies and reconstructions have lowered these estimates to 7.5-13.5 m (Mackintosh et al, 2011;Whitehouse et al, 2012a;Golledge et al, 2012Golledge et al, , 2014Gomez et al, 2013;Argus et al, 2014b;Briggs et al, 2014;Maris et al, 2014;Sutter et al, 2019). Several factors have contributed to a decrease in the estimate of the LGM AIS volume.…”

“…Ice-sheet models thus use friction formulations that can range from linear viscous and regularized Coulomb friction laws, typical of hard bedrock sliding (Larour et al, 2012;Pattyn et al, 2013;Joughin et al, 2019) to Coulomb-plastic deformation, characteristic of ice flow over a soft bedrock with filled cavities (Schoof, 2005(Schoof, , 2006Nowicki et al, 2013). In the simplest cases a constant friction coefficient is prescribed over the whole domain (Golledge et al, 2012), but generally this parameter incorporates the dependency of basal friction on the effective pressure exerted by the ice, as well as on bedrock characteristics by making use of assumed till properties (Winkelmann et al, 2011;Albrecht et al, 2019;Sutter et al, 2019) or basal temperature conditions (Pattyn, 2017;Quiquet et al, 2018). The sensitivity of the simulated ice volume to these features is substantial.…”

“…Another commonly used method is to prescribe the LGM temperature and precipitation fields for the whole Antarctic domain from climate simulations (Briggs et al, 2013;Maris et al, 2014;Sutter et al, 2019). Output from simulations using a hierarchy of climate models has been used in the literature, from global general circulation models (GCMs) (Sutter et al, 2019), sometimes downscaled with regional models (Maris et al, 2014), to Earth System Models of Intermediate Complexity (EMICs) (Blasco et al, 2019). Briggs et al (2013) went a step forward to investigate the effect of uncertainty in the climate forcing fields by assessing the effect of the inter-model variance through an empirical orthogonal function (EOF) analysis.…”