The response of the East Antarctic ice sheet to the evolving tectonic configuration of the Transantarctic Mountains

phuybrechts [ at ]


The landscape of the Transantarctic Mountains is the result of the coupled evolution of the West Antarctic rift system and the East Antarcticice sheet. Studies of this glacial-tectonic system generally assume that the evolving surface elevation of the Transantarctic Mountains is a keydeterminant of the changing East Antarctic ice-sheet dynamics between the Miocene and today. Here, we extend previous work (Huybrechts,Ph., 1993. Glaciological modeling of the Late Cenozoic East Antarctic ice sheet: stability or dynamism? Geografiska Annaler Stockholm,75A (4), 221-238) by using numerical models of the ice sheet and lithospere to examine the impact of different bedrock surface elevations ofthe Transantarctic Mountains on ice-sheet dynamics. There are widely different interpretations of the evolution of the TransantarcticMountains from the available data, so we explore bedrock surface elevations suggested by empirical evidence in recent papers about thesensitivity of the Late Cenozoic ice sheet. The results show that the surface elevation of the individual mountain blocks has only a very localeffect on ice-sheet dynamics. The existing mountain blocks of the Transantarctic Mountains, which force inland ice to drain through troughsadjacent to the mountain blocks, were overridden by inland ice when bedrock elevations were 1 km lower. When the troughs through themountains were less well developed, in the Pliocene or Miocene, inland ice was thicker and ice-surface gradients and ice-velocities across themountains were higher. This led to more active and erosive outlet glaciers through the mountains and further development of these troughs.From these results, the key determinant of East Antarctic ice dynamics appears to be the interplay between the development of major troughsthrough the Transantarctic Mountains and rising mountain elevations. The glacial history of the central Transantarctic Mountains ranges wasvery different to that of more peripheral mountain ranges, such as the Dry Valleys and Victoria Land. The development of independent icecentres in the latter regions and the overriding of these ice centres by the main ice sheet is very sensitive to the timing of surface uplift and theparticular climate profile of the period. Conversely, the ice-surface profile across the central ranges is similar under widely different climates.The limitations of such a study stem from the necessarily schematic bedrock elevations input to the model and simplifications within themodels. At present, insufficiently detailed modelling of the impact of troughs on ice-sheet dynamics means this paper is necessarilyspeculative. However, this work points to the importance of the outlet troughs on ice-sheet dynamics, rather than simply the rising surfaceelevations of the Transantarctic Mountains along the rift margin upwarp.

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Kerr, A. and Huybrechts, P. (1999): The response of the East Antarctic ice sheet to the evolving tectonic configuration of the Transantarctic Mountains , Global and Planetary Change, 23 , pp. 213-229 .

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