Glaciology and geological signature of the Last Glacial Maxi

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TitleGlaciology and geological signature of the Last Glacial Maximum Antarctic ice sheetAbstractDynamical changes in contemporary ice sheets account for significant proportions of their current rates of mass loss, but assessing whether or not these processes are a natural part of ice-sheet evolution requires inference from palaeo-glaciological records. However, a robust mechanism for translating sparse geological data into meaningful interpretations of past glacier dynamics at the continental scale is lacking, since geological archives can be ambiguous, and often their chronology is only poorly constrained. To address this, we combine the interpretation of high-resolution Antarctic ice sheet model results with continent-wide geological evidence pertinent to the dynamical configuration of the ice sheet during the last, and possibly preceding, glacial maxima. We first focus on the thermal regime of the ice sheet, its pattern and velocity of flow, variability in likely subglacial erosion and sediment transport, and how these characteristics evolve during glacial transitions. We show that rapid basal sliding was restricted to discrete outlets that eroded and advected sediment toward and across the continental shelf primarily during the early stages of advance and retreat of the ice sheet, highlighting the need to consider time-transgressive behaviour in the interpretation of geological archives. Secondly, we present new modelling that attempts to improve the fit of our numerical model to geologically-based reconstructions in the Ross Sea. By accounting for locally-enhanced ablation in McMurdo Sound, our new simulation achieves a much closer fit to empirically-derived flow patterns than previously. Growth of the modelled Last Glacial Maximum ice sheet takes place primarily by marine ice accretion in the major embayments, as a consequence of cooler ocean temperatures and reduced sub-ice-shelf melting, and at its maximal extent represents a grounded ice volume excess above present of approximately 8.3m sea-level equivalent. This figure thus provides an upper bound on the possible Antarctic contribution to deglacial meltwater pulses. Copyright 2013 Elsevier Ltd.AcknowledgementsWe are grateful to Ed Bueler, Constantine Khroulev & Andy Aschwanden for ongoing PISM support, and to Kevin Buckley for access to and assistance with the VUW compute cluster. Discussions with Sarah Greenwood and Craig Stewart proved helpful in evolving some of the ideas presented in this paper. Stephen Livingstone kindly provided digitised LGM limits. NRG acknowledges financial support from VUW Foundation grant ARCCIM. NRG and RHL are grateful to GNS Science and the ANDRILL project for support. CJF is supported by Australian Research Council Fellowships FL100100195 and FT120100004. GHD and BLH acknowledge support from the National Science Foundation. We are grateful to the anonymous reviewers for comments that helped refine the manuscript.Funding DetailsFL100100195, ARC, Australian Research Council; FT120100004, ARC, Australian Research Council; NSF, National Science Foundation

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1st AuthorGolledge, N.AuthorGolledge, N.Levy, R.McKay, R.Fogwill, C.White, D.Graham, A.Smith, J.Hillenbrand, C.-D.Licht, K.Denton, G.Ackert, R.Maas, S.Hall, B.Year2013JournalQuaternary Science ReviewsVolume78Pages225-247DOI10.1016/j.quascirev.2013.08.011URLhttps://www.scopus.com/inward/recor.....6cdef78fff64ddd8fda7d4239KeywordsAntarctic ice sheetsContinental scaleContinental shelvesErosion and sediment transportsLast Glacial MaximumOcean temperaturePlio-pleistoceneRobust mechanisms, ErosionGlacial geologyIceSea levelSediment transport, Glaciers, deglaciationevolutionflow modelingglacial hydrologyglaciologyice sheetLast Glacial Maximumsea levelsimulation, Southern Ocean, rank3Author KeywordsGlacial geologyIce-sheet modellingPlio-PleistoceneSubglacial erosion

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TypeArticleCitationGolledge, N., Levy, R., McKay, R., Fogwill, C., White, D., Graham, A., Smith, J., Hillenbrand, C.-D., Licht, K., Denton, G., Ackert, R., Maas, S. and Hall, B. (2013). Glaciology and geological signature of the Last Glacial Maximum Antarctic ice sheet. Quaternary Science Reviews, 78: 225-247IdentifierGolledge2013Relevancerank3