Where might we find evidence of a Last Interglacial West Antarctic ice sheet collapse in Antarctic ice core records?

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• Sarah Bradley, Department of Earth Sciences, University of Bristol, Bristol, UK
• Tuesday 29 May 2012, 15:30-16:30
• room 307, British Antarctic Survey, High Cross, Cambridge, CB3 0ET.

If you have a question about this talk, please contact Dr. Ailsa Benton.

If external to BAS, please email the organiser in advance to gain access to the building.

Despite numerous studies exploring the evolution of the West Antarctic Ice sheet (WAIS) during the Last Interglacial (LIG), when it is widely believed to have significant reduced in size compared to the Holocene, major uncertainties and unknowns are still left unresolved: Did the WAIS fully collapse and if so, what caused and how rapid was this collapse? What would be the impact and its contribution to the higher than present global mean sea level?

Understanding and constraining the spatial and temporal history of the WAIS during this period is complicated due to sparse amount of direct evidence. Most previous studies have relied upon indirect data records, such as far-field sea level data (Kopp et al., 2009) or paleoclimatic data (oceanic or δ180 record) (McKay et al., 2011; Menviel et al., 2010). However, these data records are sensitive not only to the impact of changes in the WAIS but to multiple signals/processes in the climate system and this suggests that a new approach is needed to address many of these remaining questions.

This study uses a different methodology to explore these issues by comparing for the first time, East Antarctic stable isotope ice core records (δD) for the LIG with the output from a glacial-isostatic adjustment (GIA) model. Results of a sensitivity study are presented which investigated if isostatically driven changes in surface elevation from a number of idealised models for the WAIS retreat will generate a resolvable and significant δD signal at these ice core sites. This is the first time this approach has been taken to seek evidence for the evolution of the WAIS during the LIG .

It will be shown that a simulated collapse of the WAIS does not generate a significant elevation-driven δD signal at the East Antarctic LIG ice core sites and as such, these ice core records cannot be used to assess WAIS stability over this period. However, treasure maps of the predicted δD and associated change in surface elevation are presented to identify regions which are sensitive to the isostatic signal associated with the WAIS collapse. These maps could be used by the wider community/field scientists to highlight sites where new data records obtained from geological studies (such as exposure ages) and/or new paleoclimatic data (such as ice core reconstructions) could constrain the evolution of the WAIS during the LIG .

Kopp, R.E., Simons, F.J., Mitrovica, J.X., Maloof, A.C. and Oppenheimer, M., 2009. Probabilistic assessment of sea level during the last interglacial stage. Nature, 462(7275), 863-867. McKay, N.P., Overpeck, J.T. and Otto-Bliesner, B.L., 2011. The role of ocean thermal expansion in Last Interglacial sea level rise. Geophysical Research Letters, 38, 6. Menviel, L., Timmermann, A., Timm, O.E. and Mouchet, A., 2010. Climate and biogeochemical response to a rapid melting of the West Antarctic Ice Sheet during interglacials and implications for future climate. Paleoceanography, 25, 12

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