Glacial melting in Antarctica may become irreversible

Glacial melting in Antarctica may become irreversible

SOURCE: The Guardian DATE: July 9, 2019 SNIP: Antarctica faces a tipping point where glacial melting will accelerate and become irreversible even if global heating eases, research suggests. A Nasa-funded study found instability in the Thwaites glacier meant there would probably come a point when it was impossible to stop it flowing into the sea and triggering a 50cm sea level rise. Other Antarctic glaciers were likely to be similarly unstable. Recent research found the rate of ice loss from five Antarctic glaciers had doubled in six years and was five times faster than in the 1990s. Ice loss is spreading from the coast into the continent’s interior, with a reduction of more than 100 metres in thickness at some sites. The Thwaites glacier, part of the West Antarctic ice sheet, is believed to pose the greatest risk for rapid future sea level rise. Research recently published in the Proceedings of the National Academy of Sciences journal found it was likely to succumb to instability linked to the retreat of its grounding line on the seabed that would lead to it shedding ice faster than previously expected. Alex Robel, an assistant professor at the US Georgia Institute of Technology and the study’s leader, said if instability was triggered, the ice sheet could be lost in the space of 150 years, even if temperatures stopped rising. “It will keep going by itself and that’s the worry,” he said. Modelling simulations suggested extensive ice loss would start in 600 years but the researchers said it could occur sooner depending on the pace of global heating and nature of the...
‘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...
Antarctic krill: Key food source moves south

Antarctic krill: Key food source moves south

SOURCE: BBC DATE: January 21, 2019 SNIP: A keystone prey species in the Southern Ocean is retreating towards the Antarctic because of climate change. Krill are small, shrimp-like creatures that swarm in vast numbers and form a major part of the diets of whales, penguins, seabirds, seals and fish. Scientists say warming conditions in recent decades have led to the krill contracting poleward. If the shift is maintained, it will have negative ecosystem impacts, they warn. Already there is some evidence that macaroni penguins and fur seals may be finding it harder to get enough of the krill to support their...
Underwater melting of Antarctic ice far greater than thought, study finds

Underwater melting of Antarctic ice far greater than thought, study finds

SOURCE: The Guardian DATE: April 2, 2018 SNIP: Hidden underwater melt-off in the Antarctic is doubling every 20 years and could soon overtake Greenland to become the biggest source of sea-level rise, according to the first complete underwater map of the world’s largest body of ice. Warming waters have caused the base of ice near the ocean floor around the south pole to shrink by 1,463 square kilometres – an area the size of Greater London – between 2010 and 2016. The research by the UK Centre for Polar Observation and Modelling at the University of Leeds suggests climate change is affecting the Antarctic more than previously believed and is likely to prompt global projections of sea-level rise to be revised upward. “What’s happening is that Antarctica is being melted away at its base. We can’t see it, because it’s happening below the sea surface,” said Professor Andrew Shepherd, one of the authors of the paper. “The changes mean that very soon the sea-level contribution from Antarctica could outstrip that from...
Antarctica Is Melting, and Giant Ice Cracks Are Just the Start

Antarctica Is Melting, and Giant Ice Cracks Are Just the Start

SOURCE: National Geographic DATE: June 28, 2017 SNIP: Seen from above, the Pine Island Ice Shelf is a slow-motion train wreck. Its buckled surface is scarred by thousands of large crevasses. Its edges are shredded by rifts a quarter mile across. In 2015 and 2016 a 225-square-mile chunk of it broke off the end and drifted away on the Amundsen Sea. The water there has warmed by more than a degree Fahrenheit over the past few decades, and the rate at which ice is melting and calving has quadrupled. On the Antarctic Peninsula, the warming has been far greater—nearly five degrees on average. That’s why a Delaware-size iceberg is poised to break off the Larsen C Ice Shelf and why smaller ice shelves on the peninsula have long since disintegrated entirely into the waters of the Weddell Sea. But around the Amundsen Sea, a thousand miles to the southwest on the Pacific coast of Antarctica, the glaciers are far larger and the stakes far higher. They affect the entire planet. “These are the fastest retreating glaciers on the face of the Earth,” says Eric Rignot, a glaciologist at the NASA Jet Propulsion Laboratory in Pasadena,...