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New lake may hold the entire history of an Antarctic ice sheet

One might assume that a two-mile high glacial sheet in the eastern Antarctic would be resting on solid rock below. However, a recent study has revealed the presence of a lake underneath a section of this ice sheet, a lake that lies at the bottom of a mile-deep canyon. 

Scientists used sophisticated instruments on board a polar research aircraft to survey the underside of the world’s largest ice sheet, in Princess Elizabeth Land on the east of Antarctica. The task took them three years to complete and this was how they identified the presence of the deep canyon running under the ice sheet, with a large lake at its base. They named the lake after the research plane that enabled them to identify the feature – Lake Snow Eagle. 

Initially, the scientists were alerted by an unusual smooth depression that appeared on satellite images of the ice sheet. In order to confirm the nature of this feature, they conducted systematic flights over the site, surveying it with ice penetrating radar and sensors that measure minute changes in Earth’s gravity and magnetic field. 

Study lead author Shuai Yan is a graduate student in the Jackson School of Geosciences at UT Austin. He was the flight planner for the field research that investigated the lake. “I literally jumped when I first saw that bright radar reflection,” said Yan.

What Yan saw was evidence of the lake’s water that, unlike ice, reflects radar like a mirror. Along with the gravity and magnetic surveys, which lit up the underlying geology of the region and the depth of water and sediments, Yan constructed a detailed picture of a jagged, highland topography with Lake Snow Eagle nestled at the base of a canyon. 

The lake measures about 30 miles in length, is nine miles wide, and has a depth of around 650 feet. But what excited the scientists most was the fact that the sediments at the bottom of the lake are 1,000 feet deep and might contain river deposits that are older than the ice sheet itself. Such sediments would give a history of the ice sheet since its earliest beginnings and this would help scientists understand what Antarctica was like before it froze and how climate change has affected it over time.

“This lake is likely to have a record of the entire history of the East Antarctic Ice Sheet, its initiation over 34 million years ago, as well as its growth and evolution across glacial cycles since then,” said study co-author and polar expert Don Blankenship. “Our observations also suggest that the ice sheet changed significantly about 10,000 years ago, although we have no idea why.”

In future, the researchers wish to drill into the sediment in order to extract cores that may fill in the gaps in understanding about Antarctica’s glaciation history. In addition, this may provide vital information about how the ice sheet will behave as the climate warms in future. 

“This lake’s been accumulating sediment over a very long time, potentially taking us through the period when Antarctica had no ice at all, to when it went into deep freeze,” said co-author Martin Siegert, a glaciologist at Imperial College London. “We don’t have a single record of all those events in one place, but the sediments at the bottom of this lake could be ideal.”

Lake Snow Eagle is one of many features uncovered by ICECAP-2, an international collaboration to map the last unknown regions of East Antarctica by polar research teams from the U.S., U.K., China, Australia, Brazil and India. The team for this paper included scientists from UTIG, Scripps Institute for Oceanography, Imperial College London, the Australian Antarctic Division, and the Polar Research Institute of China. The research was supported by the G. Unger Vetlesen Foundation and funded by governments and institutions of the countries involved.

By Alison Bosman, Staff Writer

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