Some of the last white patches on the solid surface of the earth are hidden under Antarctica’s kilometer-thick ice sheet: a working group led by Shuai Yan from the University of Texas in Austin, using various technical devices, succeeded in making at least the subsoil of a region in East Antarctica visible. As the team writes in “Geology,” the Princess Elizabeth Land site contains a large lake: its dimensions are roughly between those of Lake Chiem and Lake Constance, and the sediments deposited within it could help elucidate the history of the mighty East Antarctic Ice Sheet.
The body of water, known as Snow Lake, extends about three kilometers deep under the ice over a length of 42 kilometers, with a maximum width of 15 kilometers and a depth of about 200 meters. Yan and Co deduce that the lake contains about 21 cubic kilometers of water. It is located in a deep canyon that is also completely covered by ice.
The scientists first noticed the lake and the canyon on satellite images when they discovered a smooth depression in the otherwise irregularly shaped inland ice. They then flew over the area for three years in a special aircraft equipped with ice radar and various sensors that measure tiny changes in the Earth’s gravity and magnetic field. “I literally jumped when I first saw this bright radar reflection,” says Yan: Unlike the glacier ice, the water of the lake reflects radar waves like a mirror.
The working group is particularly interested in the sediments of Snow Lake, which are more than 300 meters thick. “This lake likely contains clues to the entire history of the East Antarctic Ice Sheet, its formation over 34 million years ago, and its growth and evolution over glacial cycles,” says Don Blankenburg, who was involved in the study. The deposits could help solve a mystery: “Our observations also indicate that the ice sheet changed significantly around 10,000 years ago, although we don’t know why.”