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Ice layers in Antarctica hold secrets to the global climate past

Sampling blue ice

A team of scientists from the Bureau of Geology has spent many Antarctic summers sampling layers of volcanic ash trapped between layers of ice to learn about climate conditions that existed at the time of the ice deposition. While the volcanic ash can be dated to constrain the time of deposition, oxygen isotope signatures in the ice reveal clues about temperatures that existed as the layers were deposited. Usually, ice climate records are obtained from samples retrieved by expensive vertical drill cores. On a trip to the West Antarctica Ice Sheet, Dr. Nelia Dunbar (geochemist) noticed that a part of a glacier had turned on edge as it flowed against a volcano called Mt. Moulton, exposing a wealth of past climate records. In 1996, she returned to do some preliminary sampling of horizontal ice cores and found that the exposed climate records date back 480,000 years ago. In November 1999, Dr. Dunbar, together with Dr. Bill McIntosh (volcanologist/geochronologist), and Rich Esser (former geochronology technician) returned with the support of an NSF grant to do extensive sampling of the upturned ice layers. Geochronological analyses of the interbedded ash will be performed in the state-of-the-art Geochronology Laboratory at New Mexico Tech.

This very long climate record may unlock secrets of the past and hint at what may develop in the future, if past warming patterns repeat themselves. Of particular interest might be the temperature data from 120,000 years ago, because some scientists think that this time period is how often a warm spell occurs. Concerns about global warming range from the potential melting of ice sheets and flooding of populated coastlines to altered weather patterns even in semi-arid New Mexico. While the ice layers won't reveal whether sea levels rose 120,000 years ago, the detailed temperature records will be valuable to compare with records being developed now.

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