City-sized lake found miles below Antarctica’s biggest ice sheet
Scientists have discovered a citysized lake hidden deep underneath the world’s largest ice sheet, and it could unlock the secrets of the sheet’s 34-million-year history. The hidden lake – which has been named Lake Snow Eagle after one of the Chinese aircraft that discovered it – lies in a mile-deep canyon beneath two miles of ice in the highlands of Princess Elizabeth Land on the East Antarctic Ice Sheet. The lake has a surface area of 143 square miles, making it one of the largest subglacial lakes beneath Antarctica’s plentiful ice.
Polar experts discovered the lake following three years of exhaustive aerial surveys over the sheet, which they peered through using radar and special sensors designed to measure minuscule changes in Earth’s gravity and its magnetic field. As the buried lake is located just a few hundred miles from the edge of the ice sheet, scientists believe it could contain 34-million-yearold river sediments – older than the ice sheet itself. If they’re right about the ancient sediments and are able to find them, the scientists could discover a treasure trove of information about what Antarctica was like before it froze, how it
has been altered by climate change and what an increasingly warming world means for its future.
“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 Don Blankenship, a senior research scientist at the University of Texas at Austin’s Institute for Geophysics. “Our observations also suggest that the ice sheet changed significantly about 10,000 years ago, although we have no idea why.”
Scientists got their first clue to the lake’s existence after spotting a smooth depression in satellite images taken of the ice sheet. Suspecting that something might be hiding underneath, the researchers mounted aeroplanes with ice-penetrating radar equipment and flew them over the sheet, scanning as they went. Because water, unlike ice, reflects radio waves like a mirror, the radar’s signal bounced back, confirming the lake’s existence.
After the researchers’ thrilling discovery of the underwater lake, flybys in aircraft equipped with gravimeters and magnetometers measured subtle changes to the gravitational and magnetic tugs given by Earth to the planes above as they flew over different parts of the sheet. This enabled the scientists to painstakingly detail the ice sheet’s underlying geometry, revealing a deeply buried lake that was 30 miles long, nine miles wide and 150 to 200 metres deep. The lake contains roughly five cubic miles of water and, most probably, a bounty of ancient sediment.
“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 Martin Siegert, a glaciologist at Imperial College London. The researchers’ next step is to get to the sediment, but as it’s sealed inside several miles of ice in the coldest region on Earth, getting there will be tricky. What’s trapped inside might not only help scientists to understand how a changing climate made the ice sheets, but how human-caused climate change could unmake them.