Limited Retreat of the Wilkes Basin Ice Sheet during the Last Interglacial.

Johannes Sutter,Hubertus Fischer,Olaf Eisen,Thomas Kleiner,Klaus Grosfeld,Martin Werner

doi:10.5194/egusphere-egu2020-13504

Johannes Sutter, Hubertus Fischer + Show 4 more

Open Access

https://doi.org/10.5194/egusphere-egu2020-13504

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Abstract

&lt;p&gt;The response of the marine sectors of the East Antarctic Ice Sheet to future global warming represents a major source of uncertainty in sea level projections. If greenhouse gas emissions continue unbridled, ice loss in these areas may contribute up to several meters to long-term global sea level rise. In East Antarctica, thinning of the ice cover of the George V and Sabrina Coast is currently taking place, and its destabilization in past warm climate periods has been implied. The extent of such past interglacial retreat episodes cannot yet be quantitatively derived from paleo proxy records alone. Ice sheet modelling constrained by paleo observations is therefore critical to assess the stability of the East Antarctic Ice Sheet during warmer climates. We propose that a runaway retreat during the Last Interglacial of the George V Coast grounding line into the Wilkes Subglacial Basin would either leave a clear imprint on the water isotope composition in the neighbouring Talos Dome ice-core record or prohibit the preservation of an ice core record from the Last Interglacial alltogether. We test this hypothesis using a dynamic ice sheet model and infer that the marine Wilkes Basin ice sheet remained stable throughout the Last Interglacial (130,000-120,000 years ago). Our analysis provides the first constraint on Last Interglacial East Antarctic grounding line stability by benchmarking ice sheet model simulations with ice core records. Our findings also imply that ambitious mitigation efforts keeping global temperature rise in check could safeguard this region from irreversible ice loss in the long term.&lt;/p&gt;

Highlights

The marine‐based sectors of the West Antarctic Ice Sheet (WAIS) and East Antarctic Ice Sheet (EAIS) are vulnerable to ocean warming and could be destabilized by processes such as hydrofracturing of ice shelves, ice cliff failure, and elevated basal melting at the grounding line
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
The large potential contribution to sea‐level rise of the EAIS is indicated by reconstructions of sea‐level highstands well beyond 10 m for the mid‐Pliocene climate optimum (Dumitru et al, 2019; Grant et al, 2019; Miller et al, 2012), which implies a retreated ice margin of the EAIS during this period

Summary

Introduction

The marine‐based sectors of the West Antarctic Ice Sheet (WAIS) and East Antarctic Ice Sheet (EAIS) are vulnerable to ocean warming and could be destabilized by processes such as hydrofracturing of ice shelves, ice cliff failure, and elevated basal melting at the grounding line. The large potential contribution to sea‐level rise of the EAIS is indicated by reconstructions of sea‐level highstands well beyond 10 m for the mid‐Pliocene climate optimum (Dumitru et al, 2019; Grant et al, 2019; Miller et al, 2012), which implies a retreated ice margin of the EAIS during this period (theoretically, the Greenland Ice Sheet and WAIS in concert with land‐based glaciers and thermal expansion of the oceans could add ∼10 m to global sea level). Uncertainties of sea‐level reconstructions going far back in time can be substantial (Rovere et al, 2014) It remains an open question whether contributions from the Wilkes and Aurora Basin were playing a major role in late Quaternary (last 400,000 years) sea‐level highstands or whether sea‐level rise was mainly driven by West Antarctic Ice Sheet collapse and melt‐back of the Greenland Ice Sheet (Dutton et al, 2015) during that time period. This would place end of century ocean warming well within reach of estimated tipping points of both the WAIS and the EAIS (Fischer et al, 2018)

TALDICE, Recorder of Potential Ice Sheet Instabilities

Forcing East Antarctic Ice Sheet Retreat During the LIG

Bistable State of the George V Coast Ice Margin During the LIG

Imprint of Wilkes Basin Ice Sheet Collapse on the TALDICE Record

Conclusions

Data Availability Statement