HR: 14:10h
AN: C33D-03    [Abstracts]
TI: Mechanisms for the Survival of Subglacial Lake Vostok During the Buildup of the Antarctic Ice Sheet
AU: * Pattyn, F
EM: fpattyn@vub.ac.be
AF: Department of Geography (WE-DGGF) Vrije Universiteit Brussel, Pleinlaan 2, Brussels, 1050 Belgium
AB: There is some debate on the origin of subglacial Lake Vostok and whether the water within the present subglacial lake system contains biota that survived the buildup of the Antarctic ice sheet. One theory suggests that Lake Vostok existed as a preglacial lake before glaciation of the continent at around 15 Ma ago, survived the subsequent period of ice sheet growth, and remained stable beneath the thick ice cover to the present day (Duxbury et al., 2001, JGR 106(E1)). Another hypothesis challenges this view by stating that the early phase of buildup would have resulted in ice grounding throughout the trough which the lake now occupies (Siegert, 2004, JGR 109(E02007)). Here, I present a physical mechanism that allows for subglacial Lake Vostok to survive the buildup of the ice sheet, by taking into account the interaction of the ice sheet with the preglacial / subglacial lake. This hypothesis is supported by the fact that the surface of a preglacial lake as well as the interface between a subglacial lake and the overriding ice sheet can be regarded as a slippery spot. Model simulations -- with the 3D higher-order ice-sheet model of Pattyn (2003, JGR 108 (B8)) -- demonstrate that due to the interaction of the ice sheet with the lake surface, ice-sheet surface slopes near the edge of the ice sheet remain low, so that subglacial water is not driven out of the subglacial trough due to enhanced hydraulic potential gradients. Survival of the lake after initiation of the Antarctic ice sheet implies that possible microorganisms and their remnants within the water can be older than 5-30 Ma. It is further discussed why subglacial troughs near the edge of the Antarctic continent (such as Astrolabe subglacial basin) are at present devoid of water.
DE: 9310 Antarctica
DE: 9604 Cenozoic
DE: 3210 Modeling
DE: 1827 Glaciology (1863)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting