A team of scientists from the United States, Germany, Russia and Austria has just returned from a 6-month drilling expedition to a frozen lake in Siberia: Lake El'gygytgyn, "Lake E" for short. Lake E was created 3.6 million years ago when a meteor more than a half-mile wide hit Earth and formed an 11-mile wide crater.

There, the researchers collected the longest sediment core samples retrieved in the Arctic region. Information contained in the cores, say the scientists, is of unprecedented significance for understanding climate change in the Arctic.

Cores collected from three holes drilled under the frozen Lake E are more than 30 times longer than cores from the Greenland Ice Sheet, according to geoscientist Julie Brigham-Grette of the University of Massachusetts at Amherst, the lead U.S. scientist on the project.

The research team will compare this Arctic record with oceanic and land-based records from lower latitudes to better understand global climate change.

Nearly 3.5 tons of temperature-controlled sediment cores are being flown by special cargo plane from Siberia to St. Petersburg in early June, then on to a lab in Germany to begin analysis by paleoclimatologists. Archived core halves will arrive later at the University of Minnesota's LacCore facility, where they will be preserved in cold storage.

Brigham-Grette says the team recovered a total of 1,165 feet of sediments; the sediment record collected extends back roughly 2 million years.

"Studying high-latitude systems is of great importance to an understanding of Earth's climate at all latitudes," says Paul Filmer, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which co-funded the expedition to Lake E with NSF's Office of Polar Programs. "Of primary interest is determining why and how the Arctic evolved from a warm forested ecosystem to a cold permafrost ecosystem between two and three million years ago." The continuous record collected in this unique lake "offers us a way to look at the glacial/interglacial climate change of the past," Brigham-Grette says.

Below the lake's sediments, cores drilled into bedrock will offer geologists a rare opportunity to study meteor impact melt rocks from one of the best preserved large meteor impact craters on Earth, and the only one formed in silicon-rich volcanic rock.

Obtaining the Cores

The logistically very challenging drilling project was successfully concluded during the first half of May 2009. The drill cores that were recovered will help to understand the details of the crater formation process. In total, the drilling reached a depth of 1,697 feet below the lake floor, or a total depth, from the lake surface, of nearly 2,255 feet.

On April 14, 2009, at a depth of about 1,023 feet below the lake floor (total depth, 1,581 ft.), the drilling reached the transition zones between the post-impact lake sediments and the impact breccia deposits, which also represented the time marker of 3.6 million years. This important moment was preceded by a long and difficult process.

Just the planning of this project – from the scientific concept to the logistical planning, application for funding, and obtaining all the necessary permits – took more than 8 years. Several hundred tons of equipment had to be transported to the very remote drilling location.

The closest town is Pevek at the Arctic Ocean, at a distance of about 217 miles from the drill site. In Pevek are a port, which is ice-free only for a few months in the summer, and an airport, which is connected to Moscow by only one flight every 2 weeks. The complete drilling equipment was sent by ship to Pevek during the summer of 2008, and then transported over land on a specially constructed snow road to the El’gygytgyn lake. Personnel and scientists, as well as sensitive equipment, were transported to the lake by cargo helicopter.

Drilling was done from the top of the frozen lake, where it turned out, for example, that the actual ice sheet had to be strengthened by pumping more water to the surface where it froze to increase the ice thickness, so that the about 75-ton drilling platform and all the supporting vehicles were safe above the 557-foot-deep lake.

Temperatures down to -22 degrees F and snowstorms with winds up to 62 mph, resulting in wind-chill factors of -58 degrees F, made the work difficult at times. In total, the drilling costs alone were about $10 million.

Christian Koeberl, head of the Department of Lithospheric Studies at the University of Vienna, also recently returned from the expedition. He is one of the principal investigators of the drilling project at El’gygytgyn, and he will be coordinating the investigation of the impact drill cores.

Results

The team recovered roughly 131 feet of the earliest history of the lake in the warm middle Pliocene. This geologic time interval is fascinating, says Brigham-Grette, as a possible analog for future climate.

Initial results from the drilling still are limited. The sediment cores could not opened in the field because of the remoteness of the drilling site and rough transportation overland. During pilot coring in November, the scientists recovered 462 feet of sediments, showing alluvial fan and lake deposits in permafrost at the western edge of the lake outside the talik (unfrozen ground in an area of permafrost).

After drilling, the borehole was permanently instrumented for future ground temperature monitoring as part of the Global Terrestrial Network for Permafrost.