Huge cavity in Antarctic glacier signals rapid decay

Huge cavity in Antarctic glacier signals rapid decay

SOURCE: NASA and Science Alert DATE: January 30, 2019 SNIP: A gigantic cavity – two-thirds the area of Manhattan and almost 1,000 feet (300 meters) tall – growing at the bottom of Thwaites Glacier in West Antarctica is one of several disturbing discoveries reported in a new NASA-led study of the disintegrating glacier. The findings highlight the need for detailed observations of Antarctic glaciers’ undersides in calculating how fast global sea levels will rise in response to climate change. Researchers expected to find some gaps between ice and bedrock at Thwaites’ bottom where ocean water could flow in and melt the glacier from below. The size and explosive growth rate of the newfound hole, however, surprised them. It’s big enough to have contained 14 billion tons of ice, and most of that ice melted over the last three years. “[The size of] a cavity under a glacier plays an important role in melting,” said the study’s lead author, Pietro Milillo of JPL. “As more heat and water get under the glacier, it melts faster.” About the size of Florida, Thwaites Glacier is currently responsible for approximately 4 percent of global sea level rise. It holds enough ice to raise the world ocean a little over 2 feet (65 centimeters) and backstops neighboring glaciers that would raise sea levels an additional 8 feet (2.4 meters) if all the ice were...
Antarctica losing six times more ice mass annually now than 40 years ago

Antarctica losing six times more ice mass annually now than 40 years ago

SOURCE: Science Daily and PNAS DATE: January 14, 2019 SNIP: Antarctica experienced a sixfold increase in yearly ice mass loss between 1979 and 2017, according to a study published today in Proceedings of the National Academy of Sciences. Glaciologists from the University of California, Irvine, NASA’s Jet Propulsion Laboratory and the Netherlands’ Utrecht University additionally found that the accelerated melting caused global sea levels to rise more than half an inch during that time. “That’s just the tip of the iceberg, so to speak,” said lead author Eric Rignot, Donald Bren Professor and chair of Earth system science at UCI. “As the Antarctic ice sheet continues to melt away, we expect multi-meter sea level rise from Antarctica in the coming centuries.” The team was able to discern that between 1979 and 1990, Antarctica shed an average of 40 gigatons of ice mass annually. (A gigaton is 1 billion tons.) From 2009 to 2017, about 252 gigatons per year were lost. The pace of melting rose dramatically over the four-decade period. From 1979 to 2001, it was an average of 48 gigatons annually per decade. The rate jumped 280 percent to 134 gigatons for 2001 to...
Discovery of recent Antarctic ice sheet collapse raises fears of a new global flood

Discovery of recent Antarctic ice sheet collapse raises fears of a new global flood

SOURCE: Science DATE: December 18, 2018 SNIP: Some 125,000 years ago, during the last brief warm period between ice ages, Earth was awash. Temperatures during this time, called the Eemian, were barely higher than in today’s greenhouse-warmed world. Yet proxy records show sea levels were 6 to 9 meters higher than they are today, drowning huge swaths of what is now dry land. Scientists have now identified the source of all that water: a collapse of the West Antarctic Ice Sheet. Glaciologists worry about the present-day stability of this formidable ice mass. Its base lies below sea level, at risk of being undermined by warming ocean waters, and glaciers fringing it are retreating fast. The discovery, teased out of a sediment core and reported last week at a meeting of the American Geophysical Union in Washington, D.C., validates those concerns, providing evidence that the ice sheet disappeared in the recent geological past under climate conditions similar to today’s. If the finding holds up, the world may need to prepare for sea level to rise farther and faster than expected: Once the ancient ice sheet collapse got going, some records suggest, ocean waters rose as fast as some 2.5 meters per...
East Antarctica glacial stronghold melting as seas warm

East Antarctica glacial stronghold melting as seas warm

SOURCE: The Guardian DATE: December 11, 2018 SNIP: A group of glaciers spanning an eighth of the East Antarctica coastline are being melted by the warming seas, scientists have discovered. This Antarctic region stores a vast amount of ice, which, if lost, would in the long-term raise global sea level by tens of metres and drown coastal settlements around the world. Freezing temperatures meant the East Antarctica region was until recently considered largely stable but the research indicates that the area is being affected by climate change. East Antarctica is extremely remote and relatively little studied. What happens to the glaciers will depend on how exposed to warmer water they are, and that depends on the shape of the land beneath them and the sea bed ahead of them. The discovery could mean much higher sea level rises than anticipated, said Chris Fogwill, a professor at Keele University in England, who was not part of the Nasa...
Modest warming risks ‘irreversible’ ice sheet loss, study warns

Modest warming risks ‘irreversible’ ice sheet loss, study warns

SOURCE: NewsAsia DATE: November 13, 2018 SNIP: Even modest temperature rises agreed under an international plan to limit climate disaster could see the ice caps melt enough this century for their loss to be “irreversible”, experts warned on Monday (Nov 12). Scientists have known for decades that the ice sheets of Greenland and Antarctica are shrinking, but it had been assumed that they would survive a 1.5-2°C temperature rise relatively intact. However, according to a new analysis published in the journal Nature Climate Change, even modest global warming could cause irreversible damage to the polar ice, contributing to catastrophic sea level rises. “We say that 1.5-2°C is close to the limit for which more dramatic effects may be expected from the ice sheets,” Frank Pattyn, head of the department of geosciences, Free University of Brussels and lead study author, told AFP. His team crunched data on annual temperature rises, ice sheet coverage and known melt levels and found that both Greenland and Antarctic ice sheets would reach a “tipping point” at around 2°C. “The existence of a tipping point implies that ice-sheet changes are potentially irreversible – returning to a pre-industrial climate may not stabilise the ice sheet once the tipping point has been crossed,” said Pattyn. Many models of the 1.5-2°C scenario allow for the threshold to be breached in the short term, potentially heating the planet several degrees higher, before using carbon capture and other technologies to bring temperatures back into line by 2100. The study warned against this approach, however, saying that a feedback loop set off by higher temperatures would “lead to self-sustained melting of...