Lost world frozen 14m years ago found in Antarctica

A lost world has been found in Antarctica, preserved just the way it was when it was frozen in time some 14 million years ago.
The fossils of plants and animals high in the mountains is an extremely rare find in the continent, one that also gives a glimpse of a what could be there in a century or two as the planet warms.


Mt Boreas in the western Olympus Range, Dry Valleys (left) and moss mat (right),
the Dry Valleys climate prevented decomposition

A team working in an ice-free region has discovered the trove of ancient life in what must have been the last traces of tundra on the interior of the southernmost continent before temperatures began to drop relentlessly.

An abrupt and dramatic climate cooling of 8°C in 200,000 years forced the extinction of tundra plants and insects and brought interior Antarctica into a perpetual deep-freeze from which it has never emerged, though may do again as a result of climate change.

An international team led by Prof David Marchant, at Boston University and Profs Allan Ashworth and Adam Lewis, at North Dakota State University, combined evidence from glaciers, from the preserved ecology, volcanic ashes and modelling to reveal the full extent of the big freeze in a part of Antarctica called the Dry Valleys.

The new insight in the understanding of Antarctica's climatic history, which saw it change from a climate like that of South Georgia to one similar to that seen today in Mars, is published in the Proceedings of the National Academy of Sciences.

"We've documented the timing and the magnitude of a tremendous change in Antarctic climate," said Prof Marchant.

"The fossil finds allow us to examine Antarctica as it existed just prior to climate cooling at 13.9 million years ago. It is a unique window into the past. To study these deposits is akin to strolling across the Dry Valleys 14.1 million years ago."

The discovery of lake deposits with perfectly preserved fossils of mosses, diatoms and minute crustacea called ostracods is particularly exciting, noted Prof Lewis. "They are the first to be found even though scientific expeditions have been visiting the Dry Valleys since their discovery during the first Scott expedition in 1902-1903," he said.

"If we can understand how we got into this relatively cold climate phase, then that can help predict how global warming might push us back out of this phase. For the vast majority of Earth history there was no permanent ice like is common today at the poles and even the tropics at high elevation. There's been a progressive cooling going on for 50 million years to get us into this permanent-ice mode; the formation of a permanent ice sheet on Antarctica plays a big role in that cooling.

"Studies like ours that establish when and how climate thresholds were crossed along the way can be used to predict climate thresholds going the opposite direction, from cool to warm.

"Although, to be fair, we're looking at one that is very far away; warming would have to be greater than what is predicted for the next one or two centuries to cause a melting of the East Antarctic Ice Sheet. The west Antarctic Ice Sheet is much more vulnerable.

Prof Ashworth is struck by how species of diatoms and mosses are indistinguishable from living ones. Today they occur throughout the world - except Antarctica.

"To be able to identify living species amongst the fossils is phenomenal. To think that modern counterparts have survived 14 million years on Earth without any significant changes in the details of their appearances is striking. It must mean that these organisms are so well-adapted to their habitats that in spite of repeated climate changes and isolation of populations for millions of years they have not become extinct but have survived."

What caused the big freeze is unknown though theories abound and include phenomena as different as the levels of carbon dioxide in the atmosphere and tectonic shifts that affected ocean circulation.

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