Buried Ice in the Dry Valleys

Buried ice deposits represent a new and potentially far-reaching archive of atmosphere and climate on Earth extending back for many millions of years. These deposits potentially are terrestrial analogs to widespread and young buried ice on the Martian surface as identified by recent data from Mars Odyssey.

Just as earlier researchers asked whether a climate record was stored in modern ice sheets of Antarctica and Greenland, we now ask whether ancient, debris-covered glaciers in the Dry Valleys hold similar records of temperature and atmospheric change, but on timescales that are perhaps an order of magnitude greater than that for the deepest existing ice core.

We are currently evaluating the age, origin, and climatic significance of buried ice in the western Dry Valleys region. Our group and others have published evidence that the ice is over a million years in age, making it by far the oldest ice yet known on this planet. An alternative view is that the buried ice is more recent segregation ice from the in-situ freezing of groundwater. Distinguishing between these hypotheses is key to understanding Neogene climate change of Antarctica.

Our first steps toward addressing this question have shown that glacier ice, far older than in the Vostok ice core (420,000 yrs), exists in Mullins Valley, southern Victoria Land, and that it contains the typical “saw-tooth” pattern for downcore changes in dD and d18O that characterize climate change records in late Quaternary ice cores.

We have assembled a diverse research team with expertise in Antarctic geomorphology, numerical modeling, cosmogenic dating, 40Ar/39Ar analyses, ice-core analyses, and ice-core drilling technology. Ongoing goals are to: 1) understand better the surface processes that permit ice preservation, 2) test the efficacy of cosmogenic and 40Ar/39Ar analyses in dating tills above buried ice, 3) further assess the use of cosmogenic-nuclide analyses and 40Ar/39Ar analyses of ashfall deposits to date buried ice, and 4) use these data to help resolve the debate between "young" and "old" ice scenarios.

Better understanding of surface processes above buried ice on Earth will permit researchers to gain access to a record of atmospheric and climate change that could well cover intervals that predate Quaternary time. The extension to recent Mars results potentially adds valuable insight into Martian history and the potential for life on Mars.

PUBLICATIONS

Marchant, D.R., Lewis, A., Phillips, W.C., Moore, E.J., Souchez, R., and Landis, G. P. 2002. Formation of patterned-ground and sublimation till over Miocene glacier ice in Beacon Valley, Antarctica. Geological Society of America Bulletin 114, 718-730.

Schäfer, J.M., Baur, H., Denton, G.H., Ivy-Ochs, S., Marchant, D.R., Schluchter, C., and Wieler, R. 2000. The oldest ice on Earth in Beacon Valley, Antarctica: new evidence from surface exposure dating. Earth and Planetary Science Letters 179, 91-99.

Sugden, D.E., Marchant, D.R., Potter, N. Jr., Roland Souchez, Denton, G. H., Carl C. Swisher, and Jean-Louis Tison. 1995. Miocene glacier ice in Beacon Valley, Antarctica. Nature 376, 412-416.

ABSTRACTS

Potter, N., Jr., Marchant, D.R., and Denton, G.H. 2003. Distribution of the Granite Drift associated with old ice in Beacon Valley, Antarctica. Geological Society of America Abstracts with Programs 35 (6), 190-3, p. 463.

Lewis, A.R. and Marchant, D.R. 2003. Evaluating the age of buried ice in Antarctica using ashfall deposits: new insights from deposit morphology, grain shape, and LA-ICP-MS trace-element geochemistry. EOS Transactions American Geophysical Union 84(46) Fall Meeting Supplement Abstract GC31-B-0176.