Paleo-dynamics of the West Antarctic Ice Sheet from processes observed along the Pacific margin

• Main Authors: Gohl, Karsten, Uenzelmann-Neben, Gabriele, Lindeque, Ansa
• Format: Conference Object
• Language: unknown
• Published: 2013
• Subjects: Amundsen Sea; Antarctic; Bellingshausen Sea; Pacific; Ross Sea; West Antarctic Ice Sheet; Antarc*; Ice Sheet
• Online Access: https://epic.awi.de/id/eprint/32213/; https://hdl.handle.net/10013/epic.40850

Data from sparsely existing drill information and numerical model simulations suggest that the West Antarctic Ice Sheet (WAIS) has behaved in a highly dynamic fashion in response to climatic variations. The analyses of drill cores from the Ross Sea shelf, for instance, infer that the WAIS underwent partial or full collapses in Pliocene times, and possible in the Miocene, when atmospheric carbon dioxide and temperature levels reached and exceeded those predicted for the next centuries. The collection of substantial seismic and other geophysical data as well as sediment cores along the West Antarctic margin from the Ross Sea to the Amundsen and Bellingshausen Sea in the recent years allows a first quantitative comparison of glacially influenced sedimentary transport and deposition processes from shelves to the continental rise of the southernmost Pacific. Sediment drift deposits of the continental rise document stages of particular dynamic bottom-currents and associated sedimentary transport activities. Drifts in the Ross Sea deep-sea record support an inferred Oligocene WAIS expansion to the outer shelf. Observations from the Amundsen Sea indicate bottom-current activity and hence a cold climate for the late Paleogene in an area, which today lies under the influence of Antarctic Bottom Water originating in the Ross Sea. The generation of drift bodies is accompanied by the occurrence of mass transport deposits leading to the identification of a phase of strong ice sheet expansion (15-4 Ma), which was followed by less material input during the last 4 m.y. due to a change in ice regime from wet-based to dry-based. A first seismostratigraphic analysis of the Amundsen Sea Embayment shelf reveals insights into the structural architecture and shows stages of sediment deposition, erosion and transport history from pre-glacial times to early glaciation and to the last glacial periods. At least 4 km of pre-glacial strata has been eroded from the present inner shelf and coastal hinterland since the onset of glaciation by ice sheet advances. The survival of buried grounding zone wedges in the upper part of the outer shelf is consistent with the onset of a long warming phase and a retreated ice sheet in the early Pliocene as observed for the Ross Sea shelf and predicted by paleo-ice sheet models. These studies and their stratigraphic constraints will serve as a basis for future drilling operations required for an improved understanding of processes leading to West Antarctic Ice Sheet retreats mechanisms.