‘Extraordinary thinning’ of ice sheets revealed deep inside Antarctica

‘Extraordinary thinning’ of ice sheets revealed deep inside Antarctica

SOURCE: The Guardian DATE: May 16, 2019 SNIP: Ice losses are rapidly spreading deep into the interior of the Antarctic, new analysis of satellite data shows. The warming of the Southern Ocean is resulting in glaciers sliding into the sea increasingly rapidly, with ice now being lost five times faster than in the 1990s. The West Antarctic ice sheet was stable in 1992 but up to a quarter of its expanse is now thinning. More than 100 metres of ice thickness has been lost in the worst-hit places. A complete loss of the West Antarctic ice sheet would drive global sea levels up by about five metres, drowning coastal cities around the world. The current losses are doubling every decade, the scientists said, and sea level rise are now running at the extreme end of projections made just a few years ago. “From a standing start in the 1990s, thinning has spread inland progressively over the past 25 years – that is rapid in glaciological terms,” said Prof Andy Shepherd, of Leeds University in the UK, who led the study. “The speed of drawing down ice from an ice sheet used to be spoken of in geological timescales, but that has now been replaced by people’s...
Melting ice sheets release tons of methane into the atmosphere

Melting ice sheets release tons of methane into the atmosphere

SOURCE: Phys.org DATE: January 3, 2019 SNIP: The Greenland Ice Sheet emits tons of methane according to a new study, showing that subglacial biological activity impacts the atmosphere far more than previously thought. An international team of researchers led by the University of Bristol camped for three months next to the Greenland Ice Sheet, sampling the meltwater that runs off a large catchment (> 600 km2) of the Ice Sheet during the summer months. As reported in Nature, using novel sensors to measure methane in meltwater runoff in real time, they observed that methane was continuously exported from beneath the ice. They calculated that at least six tons of methane was transported to their measuring site from this portion of the Ice Sheet alone. Professor Jemma Wadham, Director of Bristol’s Cabot Institute for the Environment, who led the investigation, said: “A key finding is that much of the methane produced beneath the ice likely escapes the Greenland Ice Sheet in large, fast flowing rivers before it can be oxidized to CO2, a typical fate for methane gas which normally reduces its greenhouse warming...
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...
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...
Ice cores show Greenland’s melting is unprecedented in at least four centuries

Ice cores show Greenland’s melting is unprecedented in at least four centuries

SOURCE: The Washington Post DATE: March 28, 2018 SNIP: Scientists who crossed western Greenland with a fleet of snowmobiles, pulling up long cylinders of ice at camps a little more than a mile above sea level, have found evidence that the vast sheet of ice is melting faster than at any time in the past 450 years at least — and possibly much longer than that. That’s worrisome, because the snow that has fallen on the island over millennia — now compacted into ice — could raise sea levels by 20 feet if it completely melted. The new study is further evidence that Greenland is seeing a lot of melt in the present, but what’s novel is the ability to put that in context, said Twila Moon, a research scientist at the National Snow and Ice Data Center who studies Greenland but was not involved in the current study. “It’s just another type or form of evidence to support the fact that we’re seeing really dramatic, rapid, and probably unprecedented changes,” Moon said. Based on such research, “I am personally fully confident that we haven’t seen melt like this for 5,000 years,” Osterberg...