Neogene ice sheet cyclicity in the western Amundsen Sea Embayment evidence from seismic records

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Weigelt, E. , Gohl, K. , Uenzelmann-Neben, G. and Larter, R. (2009): Neogene ice sheet cyclicity in the western Amundsen Sea Embayment evidence from seismic records , 69. Jahrestagung der Deutschen Geophysikalischen Gesellschaft, 23.-26. Mar. 2009, Kiel .
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The dynamics of ice-sheets in response to climate changes becomes increasingly a focus of research. In this regard the glacial history of the Amundsen Sea sector of the West Antarctic Ice-Sheet (WAIS) is of particular interest. A potential deglaciation and collapse of the Thwaites and Pine Island glacier drainage basins alone would result in a global sea level rise of approximately 1.5 m. Multichannel seismic reflection profiles offer a record of the glacial development in the western Amundsen Sea Embayment during the Neogene. We identified pronounced northwest-dipping reflector series of more than 1 s TWT thickness (> 800 m) on the middle shelf indicating well layered sedimentary units. The dipping strata reveal a striking alternation of reflection-poor, almost opaque units and sequences of closely spaced, continuous reflectors. We suggest that the distinct change in reflection pattern represents marked episodes of ice sheet advance and retreat forced by climate changes. Pronounced boundaries between the acoustic units give evidence for a rapid waning and waxing of ice sheets indicating concise climate transitions. Due to the similarity with the seismic stratigraphy and the lithology in bore-hole records from the adjacent Amundsen Sea and far Ross Sea we estimated these dipping strata to have been developed since the onset of glaciation in the Miocene. On the inner and middle shelf we can identify at least four events of an ice sheet expansion. We consider the West Antarctic Ice Sheet to have responded quickly and sensitively to climate variations already throughout the Neogene.

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