Warm waters melting Antarctic ice shelves may have appeared for the first time in over 7,000 years

Warm waters melting Antarctic ice shelves may have appeared for the first time in over 7,000 years

SOURCE: The Conversation DATE: October 19, 2017 SNIP: The vast expanse of the Antarctic is a region of the world particularly vulnerable to climate change, where ice loss has the potential to significantly increase sea levels. Now, for possibly the first time in 7,000 years, a phenomenon known as “upwelling” (the upward flow of warmer ocean water to the surface), is thought to have caused recent ice shelf collapse around the continent – and the glacial thinning associated with it. The ocean surrounding Antarctica is extremely cold, but water over 300m deep, Circumpolar Deep Water (CDW), is about 3⁰C above the melting point of ice. Normally, the very cold water above keeps this away from ice shelves. But in some areas, CDW is spilling onto the shallow Antarctic continental shelf, causing the ice to thin. Ice shelf thinning has accelerated in recent decades, but the picture is not the same everywhere. While the east of the Antarctic has shown modest gains in ice thickness, the west has outstripped this with significant ice loss – up to 18% in vulnerable areas like the Amundsen and Bellingshausen...
Worrying new research finds that the ocean is cutting through a key Antarctic ice shelf

Worrying new research finds that the ocean is cutting through a key Antarctic ice shelf

SOURCE: Washington Post DATE: October 11, 2017 SNIP: A new scientific study published Tuesday has found that warm ocean water is carving an enormous channel into the underside of one of the key floating ice shelves of West Antarctica, the most vulnerable sector of the enormous ice continent. The Dotson ice shelf, which holds back two separate large glaciers, is about 1,350 square miles in area and between 1,000 and 1,600 feet thick. But on its western side, it is now only about half that thickness, said Noel Gourmelen, a researcher at the University of Edinburgh in Scotland and the lead author of the research, which was just published in Geophysical Research Letters. The reason is the same one that is believed to be shrinking glaciers and pouring ice into the ocean across West Antarctica — warm ocean water located offshore is now reaching the ice from below. “We think that this channel is actually being carved for the last 25 years,” said Gourmelen, whose research team detected the channel using satellite observations. “It’s been thinning and melting at the base for at least 25 years, and that’s where we are now.” Dotson ice shelf as a whole has been thinning at an average rate of more than eight feet per year since 1994, even as the speed of ice flowing outward through the shelf has increased by 180 percent. But the thinning in the channel has been far greater. The research calculates that 45 feet of ice thickness is being subtracted annually from the channel. The new study calculates that as a result of this highly uneven melting,...
Warm waters tripled the amount of ice lost in these Antarctic glaciers — and that’s bad for sea level rise

Warm waters tripled the amount of ice lost in these Antarctic glaciers — and that’s bad for sea level rise

SOURCE: The Verge DATE: September 26, 2017 SNIP: Between 2008 and 2012, warmer than usual waters caused four glaciers in Western Antarctica to flow toward the sea faster than any other glacier on the continent. The glaciers also lost more than three times the amount of ice than usual, according to new research. All these changes are bad news for Antarctica — and us. As grounded glaciers melt, sea levels around the world rise. Researchers at NASA’s Jet Propulsion Laboratory (JPL) found that 1 to 2 degrees Fahrenheit warmer than usual waters in the area doubled the glaciers’ speed toward the sea, and more than tripled the amount of ice they lost — up to 33 feet a year, from 7 to 10 feet a year. Today’s study is the first one to show that warmer waters aren’t just affecting floating ice — they’re already also causing melting in those grounded glaciers that have the potential to raise sea levels, says study co-author Catherine Walker, a NASA postdoctoral fellow at JPL. “This is the first time that we could see something directly affecting glaciers that are on land, that are in contact with the ocean but not floating,” Walker tells The...
A key Antarctic glacier just lost a huge piece of ice — the latest sign of its worrying retreat

A key Antarctic glacier just lost a huge piece of ice — the latest sign of its worrying retreat

SOURCE: The Washington Post, Yale e360 DATE: September 25, 2017 SNIP: An enormous Antarctic glacier has given up an iceberg over 100 square miles in size, the second time in two years it has lost such a large piece in a process that has scientists wondering whether its behavior is changing for the worse. The Pine Island Glacier is one of the largest in West Antarctica, a region that is currently Antarctica’s biggest ice loser. Pine Island, which loses an extraordinary 45 billion tons of ice to the ocean each year — equivalent to 1 millimeter of global sea level rise every eight years — is 25 miles wide where its floating front touches the sea, and rests on the seafloor in waters more than a half-mile deep. The single glacier alone contains 1.7 feet of potential global sea level rise and is thought to be in a process of unstable, ongoing retreat. The glacier is feared to be in a process of unstable, runaway retreat. The grounding line has been moving inland, and as it retreats, the seafloor bed dips downward, meaning that the ocean becomes even deeper and the ice becomes even thicker. Thus, further retreat should increase the rate of outward flow and lead to even more ice...
Thirty Years After the Montreal Protocol, Solving the Ozone Problem Remains Elusive

Thirty Years After the Montreal Protocol, Solving the Ozone Problem Remains Elusive

SOURCE: Yale e360 DATE: Aug 14, 2017 SNIP: Did the Montreal Protocol fix the ozone hole? It seemed so. With chlorofluorocarbons (CFCs) and other ozone-eating chemicals banned, many scientists said it was only a matter of time before the ozone layer recharged, and the annual hole over Antarctica healed for good. But 30 years on, some atmospheric chemists are not so sure. The healing is proving painfully slow. And new discoveries about chemicals not covered by the protocol are raising fears that full recovery could be postponed into the 22nd century – or possibly even prevented altogether. …[I]n the past five years, evidence has emerged that potential ozone-eating compounds can reach the ozone layer much faster than previously thought. Under some weather conditions, just a few days may be enough. And that means a wide range of much more short-lived compounds threaten the ozone layer – chemicals not covered by the Montreal Protocol. These compounds are all around us. They are widely used as industrial solvents for tasks like degreasing and dry cleaning. And their releases into the atmosphere are increasing fast. … [Jonathan Shanklin of the British Antarctic Survey] says an important reason for the sluggish recovery of the ozone layer is global warming. As increased levels of greenhouse gases such as carbon dioxide trap more solar heat radiating from the Earth’s surface, less warmth reaches the stratosphere, which cools as a result. This trend has been evident for almost 40 years. A colder stratosphere improves conditions for ozone loss. Climate change “could delay the recovery of the ozone hole well into the second half of this century,”...