Limited Retreat of the Wilkes Basin Ice Sheet During the Last Interglacial

Abstract

The response of the East Antarctic Ice Sheet to global warming represents a major source of uncertainty in sea‐level projections. Thinning of the East Antarctic George V and Sabrina Coast ice cover is currently taking place, and regional ice‐sheet instability episodes might have been triggered in past warm climates. However, the magnitude of ice retreat in the past cannot yet be quantitatively derived from paleo‐proxy records alone. We propose that a runaway retreat of the George V coast grounding line and subsequent instability of the Wilkes Basin ice sheet would either leave a clear imprint on the water isotope composition in the Talos Dome region or prohibit a Talos Dome ice‐core record from the Last Interglacial altogether. Testing this hypothesis, our ice‐sheet model simulations suggest that Wilkes Basin ice‐sheet retreat remained relatively limited during the Last Interglacial and provide a constraint on Last Interglacial East Antarctic grounding line stability.

Retreat of the Antarctic Ice Sheet During the Last Interglaciation and Implications for Future Change

“…Steepening of the ice surface due to bedrock uplift and grounding-line retreat lead to enhancing thinning as ice is advected more quickly downglacier, eventually allowing time-separated ice layers (isochrones) to converge. change at Talos Dome from 132 to 116 ka (blue line), and indicates changes of approximately 100 m over 10,000 years, consistent with the TALDICE reconstruction (Sutter et al, 2020). We also track changes in ice elevation and basal ice velocity in the key outlet glaciers of this region: Cook, Ninnis, and Mertz (Figures 4e and 4f).…”

“…Inland terrestrial geochemical records, however, suggest that the WSB has been ice-filled since c. 400 ka BP (Blackburn et al, 2020), and hence if it did contribute to higher-than-present LIG GMSL, the contribution may have been relatively minor. Recent high-resolution ice sheet modeling as well as GCM experiments support this latter interpretation, showing that the isotopic record preserved in the Talos Dome ice core is inconsistent with the surface lowering of that area that would have occurred had the WSB deglaciated substantially (Goursaud et al, 2020;Sutter et al, 2020). Sutter et al (2020) conclude that during the LIG the WSB could have contributed only up to ca.…”

“…Whole-continent ISM reconstructions that have used environmental forcings directly from climate models without the ad hoc imposition of additional heat predict an AIS LIG contribution of 3-4.4 m (Clark et al, 2020;Goelzer et al, 2016). Whole continent as well as single catchment or limited area models have been used to investigate the sensitivity of key AIS drainage basins to both realistic and conceptual warming levels (Feldmann & Levermann, 2015;Golledge, Thomas, et al, 2017;Mengel & Levermann, 2014;Sutter et al, 2020) but the scarcity of near-field empirical evidence with which to constrain ISM simulations prevents a critical evaluation of either the AIS contribution to LIG GMSL or the robustness of the models themselves.…”

Antarctic Ice Sheet Elevation Impacts on Water Isotope Records During the Last Interglacial

“…Using our simulations, we thus look at the Δδ 18 O versus elevation relationship (LIG temporal relationship) and show that this relationship at this site is -0.93‰/100 m. For the elevation change they simulate in the case of Wilkes Basin ice collapse, using our LIG temporal relationship, this would lead to an inferred TALDICE δ 18 O increase from 11‰ to 19‰, that is, 73%-83% higher than suggested. This implied underestimation of the inferred δ 18 O from the grounding retreat, reinforces the conclusions ofSutter et al (2020), emphasizing that TALDICE is an highly sensitive site for indicating EAIS LIG changes, and exclude the Wilkes Basin loss of ice scenarios, since the TALDICE LIG-PI δ 18 O measured change is only 2‰(Masson-Delmotte et al, 2008).…”

“…A model-data (ice core) δ 18 O comparison allowed insight into the most likely LGM AIS configuration. More recently, Sutter et al (2020) derived the most probable Wilkes configuration for the LIG by comparing δ 18 O anomalies from the Talos Dome Ice Core with a suite of ice sheet model simulations using the Parallel Ice Sheet Model (Golledge et al, 2015). Sutter et al (2016) inferred the LIG δ 18 O signal for each of their model configurations using the present-day surface air temperature (SAT) versus elevation relationship from Frezzotti et al (2007) to obtain temperature, and then to apply the SAT versus temperature derived from Werner et al (2018).…”