Abstract
AbstractThe 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.
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
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
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 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
Summary
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 underlying hypothesis of this work is that a minor retreat of the George V Coast grounding line could destabilize the Wilkes Basin marine ice sheet (Mengel & Levermann, 2014) We propose that this would lead to a drastic lowering of the ice elevation in the neighboring Talos Dome region leaving an imprint in the water isotope record, which is an archive of paleo‐temperatures and sea‐ice/ice‐sheet changes (Holloway et al, 2016). The continental ice cores EPICA Dome C, Dome Fuji, and Vostok are isolated by much larger distances from the coast, which makes them relatively insensitive to grounding line migration Their low glacial‐interglacial thickness changes (Sutter et al, 2019) and stable water vapor source regions (Masson‐ Delmotte et al, 2011) make them reliable recorders of large‐scale Antarctic climate variations with small elevation change corrections to their isotope‐temperature record (see Figure 1b). To estimate the imprint of this instability on the TALDICE δ18O‐record, we convert simulated surface elevation changes to temperature assuming a lapse rate of 0.8 K/100 m (Frezzotti et al, 2007) and calculate the changes in local δ18O with a regional isotope/temperature relationship of 0.7–1.4 permil/K derived from Werner et al (2018)
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