Letter | Published:

A dynamic early East Antarctic Ice Sheet suggested by ice-covered fjord landscapes

Nature volume 474, pages 7275 (02 June 2011) | Download Citation

Abstract

The first Cenozoic ice sheets initiated in Antarctica from the Gamburtsev Subglacial Mountains1 and other highlands as a result of rapid global cooling 34 million years ago2. In the subsequent 20 million years, at a time of declining atmospheric carbon dioxide concentrations2 and an evolving Antarctic circumpolar current2, sedimentary sequence interpretation3 and numerical modelling4 suggest that cyclical periods of ice-sheet expansion to the continental margin, followed by retreat to the subglacial highlands, occurred up to thirty times. These fluctuations were paced by orbital changes and were a major influence on global sea levels5. Ice-sheet models show that the nature of such oscillations is critically dependent on the pattern and extent of Antarctic topographic lowlands. Here we show that the basal topography of the Aurora Subglacial Basin of East Antarctica, at present overlain by 2–4.5 km of ice, is characterized by a series of well-defined topographic channels within a mountain block landscape. The identification of this fjord landscape, based on new data from ice-penetrating radar, provides an improved understanding of the topography of the Aurora Subglacial Basin and its surroundings, and reveals a complex surface sculpted by a succession of ice-sheet configurations substantially different from today’s. At different stages during its fluctuations, the edge of the East Antarctic Ice Sheet lay pinned along the margins of the Aurora Subglacial Basin, the upland boundaries of which are currently above sea level and the deepest parts of which are more than 1 km below sea level. Although the timing of the channel incision remains uncertain, our results suggest that the fjord landscape was carved by at least two iceflow regimes of different scales and directions, each of which would have over-deepened existing topographic depressions, reversing valley floor slopes.

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Acknowledgements

This work was supported by NSF grant ANT-0733025 and NASA grant NNX09AR52G to the University of Texas at Austin, NERC grant NE/D003733/1 to the University of Edinburgh, Australian Antarctic Division project 3103, the Jackson School of Geoscience, and the Jet Propulsion Laboratory, and the G. Unger Vetlesen Foundation. This research was also supported by the Antarctic Climate and Ecosystems Cooperative Research Centre. This is UTIG contribution 2344.

Author information

Affiliations

  1. Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas 78758, USA

    • Duncan A. Young
    • , Jamin S. Greenbaum
    • , Dustin M. Schroeder
    • , John W. Holt
    •  & Donald D. Blankenship
  2. School of GeoSciences, University of Edinburgh, King’s Buildings, Edinburgh EH9 3JW, UK

    • Andrew P. Wright
    • , David E. Sugden
    •  & Martin J. Siegert
  3. Australian Antarctic Division, Kingston, Tasmania 7050, Australia

    • Jason L. Roberts
    • , Roland C. Warner
    • , Neal W. Young
    •  & Tas D. van Ommen
  4. Antarctic Climate & Ecosystems Cooperative Research Centre, Hobart, Tasmania 7001, Australia

    • Jason L. Roberts
    • , Roland C. Warner
    • , Neal W. Young
    •  & Tas D. van Ommen

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Contributions

D.A.Y., D.D.B., M.J.S., J.W.H., R.C.W., N.W.Y., J.L.R. and T.D.v.O. planned the investigation, including the flights. D.A.Y. and D.D.B. oversaw the data reduction. D.A.Y., D.D.B., A.P.W., J.W.H., J.S.G., D.M.S., J.L.R. and R.C.W. participated in the field work. D.E.S. and M.J.S. provided the geomorphic interpretation. D.A.Y., M.J.S., D.D.B. and A.P.W. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Duncan A. Young or Martin J. Siegert.

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DOI

https://doi.org/10.1038/nature10114

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