Icy yield: drilling at Lake El'gygytgyn has already retrieved a climate record for the past 400,000 years. Credit: O. JUSCHUS/LEIPZIG UNIV.

A preliminary excursion to a remote Russian lake has raised scientists' hopes that it will offer the most reliable terrestrial records yet of arctic climate history.

Located in the extreme northeastern tip of Siberia, Lake El'gygytgyn is unique, climate researchers say. Unlike most of the Arctic, the lake has never been covered by glaciers, which disrupt the accumulation of sediment. This means that El'gygytgyn's floor offers an uninterrupted view of past climate patterns.

“Drilling cores from the lake should provide a fantastic climate archive,” says Thomas Stocker, a climate researcher at the University of Bern in Switzerland. “It would be a valuable supplement to marine drillings, whose information is always filtered by the ocean.”

During a four-month expedition last year, geologists and limnologists from Germany, Russia and the United States probed the lake's sediments and surrounding permafrost soil to check out their likely usefulness. And at a meeting in Leipzig, Germany, late last month, they announced that their study had confirmed the lake's potential.

“Our survey has revealed that the bedding of the lake floor sediments is perfectly undisturbed,” says Marin Melles, a geologist at the University of Leipzig and member of the expedition.

The lake is now being put forward as a site for the International Continental Drilling Program, a collaboration of 11 countries that aims to extract cores from the continental shelf, which would conduct a 400-metre deep-drilling project there in 2007.

El'gygytgyn, which is about 175 metres deep and 15 kilometres across, fills the larger part of a crater created by a meteorite impact 3.6 million years ago. It is on the Chukotka peninsula, opposite Alaska, an area far from any settlement and very difficult to reach.

The expedition team and nine tonnes of equipment were flown to the lake last April by helicopter from Pevek, a small town on the East Siberian Sea.

Getting to the lake was difficult, Melles says. At first, Russian customs in St Petersburg declined to clear several items, including a snowmobile, which never made its way east. And summer evacuation from the camp, which was beginning to drown in seasonal mud, was delayed for a few days because available Russian helicopter pilots had hit statutory limits on their monthly flying hours. To get out, the researchers eventually had to hire a helicopter from a local gold-mining company.

But the scientific yield was worth the effort, says Julie Brigham-Grette, a geologist at the University of Massachusetts in Amherst. Brigham-Grette, in collaboration with Melles and with researchers at the North-East Interdisciplinary Scientific Research Institute in Magadan in far-eastern Russia, is analysing mineralogy and organic traces in the lake-floor sediments.

Seismic profiling shows that the sediments are some 400 metres thick, and probably contain an exceptional record running from the meteorite impact, in the Pliocene warm period, up to the present day. The expedition recovered a drilling core 16 metres long, representing the past 400,000 years, from the centre of the lake.

Deep drilling in Lake El'gygytgyn would help researchers study arctic climate change before the onset of glaciation 2.2 million years ago, explains Brigham-Grette.