CryoSat maps largest-ever flood beneath Antarctica

Site of crater

ESA’s CryoSat satellite has found a vast crater in Antarctica’s icy surface. Scientists believe the crater was left behind when a lake lying under about 3 km of ice suddenly drained. Far below the thick ice sheet that covers Antarctica, there are lakes of fresh water without a direct connection to the ocean. These lakes are of great interest to scientists who are trying to understand water transport and ice dynamics beneath the frozen Antarctic surface – but this information is not easy to obtain. One method is to drill holes through kilometres of ice to the water – a difficult endeavour in the harsh conditions of the polar regions. But instead of looking down towards the ice, a team of European scientists is looking to the sky to improve our understanding of subglacial water and its transport. By combining new measurements acquired by CryoSat with older data from NASA’s ICESat satellite, the team has mapped the large crater left behind by a lake, and even determined the scale of the flood that formed it. From 2007 to 2008, six cubic kilometres of water – about the same amount that is stored in Scotland’s Loch Ness – drained from

3D view

the lake, making it the largest event  of its kind ever recorded. That amount of water equals a tenth of the melting that occurs beneath Antarctica each year. Since the end of 2008, the lake appears to be refilling but six times slower than it drained. It could take decades to reform. The study, published recently in Geophysical Research Letters, highlights CryoSat’s unique capacity to map changes in Antarctica’s subglacial lakes in 3D, and sheds new light on events at the base of the ice sheet. CryoSat carries a radar altimeter that can ‘see’ through clouds and in the dark, providing continuous measurements over areas like Antarctica that are prone to bad weather and long periods of darkness. The radar can measure

ESA's ice mission CryoSat

both the area and depth of ice craters in high resolution, allowing scientists to calculate its volume accurately. “Thanks to CryoSat, we can now see fine details that were not apparent in older satellite data records,” said Dr Malcolm McMillan from the UK’s University of Leeds and lead author of the study ‘Three-dimensional mapping by CryoSat-2 of subglacial lake volume changes’. With every subglacial lake, there is hope of finding prehistoric marine life. The rapid draining and apparent refilling of this lake, however, suggests this was not the first time water has drained from the lake. “It seems likely that the flood water – and any microbes or sediments it contained – has been flushed into the Southern Ocean, making it difficult to imagine that life in this particular lake has evolved in isolation,” said Prof. Andrew Shepherd, a co-author of the study. About 400 lakes have been discovered at the base of the Antarctic ice sheet. When they drain, they disrupt subglacial habitats and can cause the ice above to slide more quickly into the sea. Source: Orbiter.ch Space News

Read More........→July 21, 2013

Beneath Antarctic Ice: Vast Canal System Found

In a development that will help predict potential sea level rise from the Antarctic ice sheet, scientists from The University of Texas at Austin’s Institute for Geophysics have used an innovation in radar analysis to accurately image the vast subglacial water system under West Antarctica’s Thwaites Glacier. They have detected a swamp-like canal system beneath the ice that is several times as large as Florida’s Everglades. Figure showing the transition from swamp-like water to stream-like water beneath Thwaites Glacier, West Antarctica. The findings, as described this week in the Proceedings of the National Academy of Sciences, use new observational techniques to address long-standing questions about subglacial water under Thwaites, a Florida-sized outlet glacier in the Amundsen Sea Embayment considered a key factor in projections of global sea level rise. On its own, Thwaites contains enough fresh water to raise oceans by about a meter, and it is a critical gateway to the majority of West Antarctica’s potential sea level contribution of about 5 meters. The new observations suggest the dynamics of the subglacial water system may be as important as well recognized ocean influences in predicting the fate of Thwaites Glacier. Without an accurate characterization of the bodies of water deep under Thwaites, scientists have offered competing theories about their existence and organization, especially in the rapidly changing region where the glacier meets the ocean. Using an innovation in airborne ice-penetrating radar analysis developed by lead author Dusty Schroeder, a doctoral candidate at the Institute for Geophysics, the Texas team shows that Thwaites’ subglacial water system consists of a swamp-like canal system several times as large as Florida’s Everglades lying under the deep interior of the ice sheet, shifting to a series of mainly stream-like channels downstream as the glacier approaches the ocean. Scientists have attempted to use ice-penetrating radar to characterize subglacial water for many years, but technical challenges related to the effects of ice temperature on radar made it difficult to confirm the extent and organization of these water systems. Schroeder’s technique looking at the geometry of reflections solves this problem, because the temperature of the ice does not affect the angular distribution of radar energy. “Looking from side angles, we found that distributed patches of water had a radar signature that was reliably distinct from stream-like channels,” said Schroeder. He compared the radar signature to light glinting off the surface of many small interconnected ponds when viewed out of an airplane window. Distinguishing subglacial swamps from streams is important because of their contrasting effect on the movement of glacial ice. Swamp-like formations tend to lubricate the ice above them whereas streams, which conduct water more efficiently, are likely to cause the base of the ice to stick between the streams. (The effect is similar to the way rain grooves on a tire can help prevent a car from hydroplaning on a wet road.) As a result of this change in slipperiness, the glacier’s massive conveyor belt of ice piles up at the zone where the subglacial water system transitions from swamps to streams. This transition forms a stability point along a subglacial ridge that holds the massive glacier on the Antarctic continent. “This is where ocean and ice sheet are at war, on that sticking point, and eventually one of them is going to win,” said co-author Don Blankenship, a senior research scientist from the Institute for Geophysics. Cartoon representations (above) and radar images (below) of the distinct swamp-like and stream-like water systems observed beneath Thwaites Glacier, West Antarctica. Observations of the subglacial stream-and-swamp dynamic and the sub-ice topography suggest that Thwaites Glacier is stable in the short term, holding its current position on the continent. However, the large pile of ice that has built up in the transition zone could rapidly collapse if undermined by the ocean warming or changes to the water system. “Like many systems, the ice can be stabilized until some external factor causes it to jump its stability point,” said Blankenship. “We now understand both how the water system is organized and where that dynamic is playing itself out. Our challenge is to begin to understand the timing and processes that will be involved when that stability is breched.” Current models predicting the fate of the glacier do not yet account for these dynamic, subglacial processes. The findings rely on radar data acquired during airborne geophysical surveys over West Antarctica by the Institute for Geophysics, with operational support from the National Science Foundation. The analysis was enabled through intensive supercomputing supported by the university’s Texas Advanced Computing Center. The research was funded through grants from the National Science Foundation and NASA, with additional support from both the Vetlesen Foundation and the Institute for Geophysics, which is a research unit of the university’s Jackson School of Geosciences. Contacts and sources: University of Texas Institute for Geophysics. Source: Nano Patents And Innovations, Image: flickr.com

Read More........→July 13, 2013

Space Penguin: The Closest Thing To A Creature From Outer Space Say Scientists

Credit: ESA

This Adélie Penguin is not from outer space but its nearest equivalent on Earth: Antarctica. The penguin was photographed at Terra Nova Bay, Antarctica by ESA-sponsored medical research doctor Vangelis Kaimakamis on one of his stopovers on the long voyage to Concordia research station in the heart of the white continent. His voyage took him from Greece to Germany, Singapore, Australia and New Zealand before arriving at McMurdo base in Antarctica. From there he transferred to the Italian Zucchelli Station at Terra Nova Bay, where weather grounded him for a week. The Adélie Penguin may have been one of the last animals Vangelis sees during his 10-month stay at Concordia because no living being can survive the harsh conditions there. With temperatures as low as –80°C, no outside help can be flown in during the winter and even the Sun does not rise above the horizon for four months. The closest base to Concordia is the Russian Vostok outpost, some 600 km away. In comparison, the International Space Station is closer to civilisation – astronauts can escape in an emergency and land in under four hours. Concordia is one of the most isolated place in the world, not unlike a martian outpost. During the Antarctic winter, a skeleton crew of 15 researchers and technicians will keep the base running in the name of science at the end of the world.Vangelis will run experiments on how people adapt to the stress of living in close isolation. The research this year will be as diverse as studying how the crew’s body posture changes and which materials are more resistant to bacterial growth. This is one of the many ways ESA is studying human physiology and psychology in preparation for future long missions beyond Earth. Follow the science and daily life of the Concordia crew as they experience the dark cold of Antarctica on the Chronicles from Concordia blog. Contacts and sources: ESA, Source: Nano Patents And Innovations

Read More........→February 07, 2013