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Fossils Reveal Much Warmer Antarctic in Recent Past

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This ostracod fossil from the Dry Valleys of Antarctica is less than 1 mm long, but preserves an array of soft tissues including legs and mouth parts.Mark Williams, University of Leicester

A college student's new discovery of fossils collected in the East Antarctic suggests that the frozen polar cap was once a much balmier place.

The well-preserved fossils of ostracods, a type of small crustacean, came from the Dry Valleys region of Antarctica's Transantarctic Mountains and date from about 14 million years ago. The fossils were a rare find, showing all of the ostracods' soft anatomy in 3-D.

The fossils were discovered by Richard Thommasson during screening of the sediment in research team member Allan Ashworth's lab at North Dakota State University.

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Because ostracods couldn't survive in the current Antarctic climate, their presence suggests that the southern-most continent hasn't always been as frigid as it is today.

"Present conditions in this Antarctic region show mean annual temperatures of minus 25 degrees C (Celsius) [minus 13 degrees Fahrenheit]," said Mark Williams of the University of Leicester, co-author with Ashworth of the fossil-find report in the journal Proceedings of the Royal Society B. "These are impossible conditions to sustain a lake fauna with ostracods."

The authors think the ostracods and the habitat they lived in were the last vestiges of a tundra ecosystem, similar to those found in Patagonia, that once thrived in Antarctic coastal regions, before an intense period of cooling gave rise to the Antarctic environment we see today.

While geologists theorize that the land that now makes up Antarctica was once a part of other continents closer to the equator — hundreds of millions of years ago — the warmer climate that supported the ostracods would have existed "when Antarctica was pretty much in its current location," said study co-author David Marchant of Boston University.

Marchant estimated that the summer temperatures in Antarctica would have been about 30.6 degrees F (17 degrees C) warmer than they are now.

This warmer period started to end when the first continent-sized ice sheets began appearing on Antarctica around 34 million years ago, around the end of the Eocene epoch.

These ice sheets expanded and contracted until around 14 million years ago, during the Miocene epoch, when a dramatic cooling took place and transformed the tundra into an environment "that today looks like Mars," Marchant told LiveScience.

Marchant said climatologists are uncertain exactly what caused this intense period of cooling.

The research was funded by the National Science Foundation.

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