Antarctic fossil find shows Antarctica was once warmer.

The National Science Foundation today released some interesting findings about the climatic history of the Antarctic.

National Science Foundation-funded scientists working in an ice-free region of Antarctica have discovered the last traces of tundra–in the form of fossilized plants and insects–on the interior of the southernmost continent before temperatures began a relentless drop millions of years ago.

An abrupt and dramatic climate cooling of 8 degrees Celsius, over a relatively brief period of geological time roughly 14 million years ago, forced the extinction of tundra plants and insects and transformed the interior of Antarctica into a perpetual deep-freeze from which it has never emerged.

The international team of scientists headed by David Marchant, an earth scientist at Boston University and Allan Ashworth and Adam Lewis, geoscientists at North Dakota State University, combined evidence from glacial geology, paleoecology, dating of volcanic ashes and computer modeling, to report a major climate change centered on 14 million years ago. The collaboration resulted in a major advance in the understanding of Antarctica’s climatic history.

NSF, in its role as the manager of the United States Antarctic Program, supported Ashworth’s, Lewis’, and Marchant’s research as well as U.S. researchers from Lamont-Doherty Earth Observatory, Ohio State University and the University of Montana.

Their findings appear in the Aug. 4 edition of the Proceedings of the National Academy of Sciences.

The discovery of lake deposits with perfectly preserved fossils of mosses, diatoms and ostracods, a type of small crustacean, is particularly exciting to scientists, noted Lewis. Fossils are extremely rare in Antarctica, especially those of terrestrial and freshwater plants and animals.

“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,” said Lewis. Robert Falcon Scott was a British Antarctic explorer who perished during an attempt to the first to reach the South Pole in 1912.

The fossil location today high in the mountains is a completely frozen landscape.

Marchant, Lewis and Ashworth, who often spend months living in tents in the Dry Valleys doing their research, all said that the fossil finds stretch their imagination about how the Antarctic continent once looked.

“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. On land, there are very few places on Earth that contain sediment of this age, and none are as well preserved as those found in the Dry Valleys,” Marchant said. “The sediments allow reconstructions of alpine glaciers, tundra and lakes, all in remarkable detail. To study these deposits is akin to strolling across the Dry Valleys 14.1 million years ago.”

The mean summertime temperatures would have dropped in that period by as much as 8 degrees Celsius. On average, the summertime temperatures in the Valleys during this temperate period would have been as much as 17 degrees warmer than the present-day average. What caused the change, Marchant said, “Is really a big 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.

According to Lewis, the freshness of the crystals and glass in the volcanic ash and the preservation of cellular detail in the fossils argues that they have been permanently frozen since 13.9 million years ago. The climate changed during those millions of years but the temperatures in the mountains never rose high enough to allow groundwater to flow and microorganisms to become active.

This conclusion suggests that even when global atmospheric temperatures were warmer than they are now, as occurred–approximately 3.5 million years ago during the Pliocene Epoch–and as might occur in the near future as a consequence of global warming, there was no significant melting of the East Antarctic ice sheet inland of the Dry Valleys, nor were there dramatic changes in environmental conditions in the fossil region.

If this conclusion stands the test of time, it suggests a very robust ice sheet in this sector of Antarctica, and stresses the complex and potentially non-uniform response of Antarctica’s ice sheets to global change.

Part of the study in the Dry Valleys is captured in the documentary “Ice People,” by Emmy-award winning director Anne Aghion. NSF’s Antarctic Artists and Writers program supported Aghion in the field for four months in 2006 to document the work of scientists there. The film is being released to coincide with the International Polar Year 2007-2009 (IPY), a global scientific deployment, and is scheduled to air on the Sundance Channel in 2009.

A video interview with David Marchant can be viewed at the National Science Foundation website at the link here.

Read the article in full at the link above along with further interesting links.

The wonderful work carried out by the National Science Foundation brings us images and information about this fascinating continent.

IMAGE:

Insects, ferns flourished, then flickered out millions of years ago as the tundra retreated

Fossils of McMurdo Dry Valleys

Examples of fossils found in the McMurdo Dry Valleys. Credit: Zina Deretsky/National Science Foundation

PHOTO OF THE DAY:

Everett Wilkerson scrambles up an aluminum ladder inside an ice cave. These caves form inside the ‘ice tongue’, a 40-foot-tall bulkhead of snow and ice that runs off the slopes of Mount Erebus on Ross Island.

ice cave Mount Erebus

Photograph by: Alexander Colhoun. National Science Foundation. Date Taken: 1998

Advertisements

~ by abstraktbiblos on Wednesday, 6 August, 2008.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: