A dynamic early East Antarctic Ice Sheet suggested by ice-covered fjord landscapes
The first Cenozoic ice sheets initiated in Antarctica from theGamburtsev Subglacial Mountains and other highlands as a resultof rapid global cooling 34 million years ago. In the subsequent 20million years, at a time of declining atmospheric carbon dioxideconcentrations and an evolving Antarctic circ...
| Published in: | Nature |
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| Main Authors: | , , , , , , , , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
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Nature Publishing Group
2011
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| Subjects: | |
| Online Access: | https://doi.org/10.1038/nature10114 http://www.ncbi.nlm.nih.gov/pubmed/21637255 http://ecite.utas.edu.au/75883 |
| Summary: | The first Cenozoic ice sheets initiated in Antarctica from theGamburtsev Subglacial Mountains and other highlands as a resultof rapid global cooling 34 million years ago. In the subsequent 20million years, at a time of declining atmospheric carbon dioxideconcentrations and an evolving Antarctic circumpolar current,sedimentary sequence interpretation and numerical modellingsuggest that cyclical periods of ice-sheet expansion to the continentalmargin, followed by retreat to the subglacial highlands, occurred upto thirty times. These fluctuations were paced by orbital changes andwere a major influence on global sea levels. Ice-sheet models showthat the nature of such oscillations is critically dependent on thepattern and extent of Antarctic topographic lowlands. Here we showthat the basal topography of the Aurora Subglacial Basin of EastAntarctica, at present overlain by 24.5km of ice, is characterizedby a series of well-defined topographic channels within a mountainblock landscape. The identification of this fjord landscape, based onnew data from ice-penetrating radar, provides an improved understandingof the topography of the Aurora Subglacial Basin and itssurroundings, and reveals a complex surface sculpted by a successionof ice-sheet configurations substantially different from todays. Atdifferent stages during its fluctuations, the edge of the EastAntarcticIce Sheet lay pinned along the margins of the Aurora SubglacialBasin, the upland boundaries of which are currently above sea leveland the deepest parts of which are more than 1km below sea level.Although the timing of the channel incision remains uncertain, ourresults suggest that the fjord landscape was carved by at least two iceflowregimes of different scales and directions, each of which wouldhave over-deepened existing topographic depressions, reversingvalley floor slopes. |
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