Antarctica's 'Doomsday Glacier' could meet its doom within 3 years
Time is melting away for one of Antarctica's biggest glaciers, and its rapid deterioration could end with the ice shelf's complete collapse in just a few years, researchers warned at a virtual press briefing on Monday (Dec. 13) at the annual meeting of the American Geophysical Union (AGU).
Thwaites glacier in western Antarctica is the widest glacier on Earth, spanning about 80 miles (120 kilometers) and extending to a depth of about 2,600 to 3,900 feet (800 to 1,200 meters) at its grounding line — where the glacier transitions from a land-attached ice mass to a floating ice shelf in the Amundsen Sea. Thwaites is sometimes referred to as the "Doomsday Glacier," as its collapse could trigger a cascade of glacial collapse in Antarctica, and the latest research from the frozen continent suggests that doomsday may be coming for the dwindling glacier even sooner than expected.
Warming ocean water is not just melting Thwaites from below; it's also loosening the glacier's grip on the submerged seamount below, making it even more unstable. As the glacier weakens, it then becomes more prone to surface fractures that could spread until the entire ice shelf shatters "like a car window" — and that could happen as soon as three years from now, researchers said at AGU, held in New Orleans and online.
海水变暖不仅使思韦茨冰川底部开始融化，同时该冰川的海底冰山部分也开始松动，使其更加不稳定。研究人员在新奥尔良举行的 AGU 会议上表示，随着冰川逐渐消融，它更容易出现表面裂缝，这种裂缝可能会逐渐蔓延，直到整个冰架像汽车车窗玻璃一样破碎，预计这些悲剧将在三年后发生。
Over the last decade, observations of Thwaites showed that the glacier is changing more dramatically than any other ice and ocean system in Antarctica, thanks to human-induced climate change and increased warming in Earth's atmosphere and oceans. Thwaites has already lost an estimated 1,000 billion tons (900 billion metric tons) of ice since 2000; its annual ice loss has doubled in the past 30 years, and it now loses approximately 50 billion tons (45 billion metric tons) more ice than it receives in snowfall per year, according to The International Thwaites Glacier Collaboration (ITGC).
If Thwaites were to break up entirely and release all its water into the ocean, sea levels worldwide would rise by more than 2 feet (65 centimeters), said ITGC lead coordinator Ted Scambos, one of the presenters at AGU and a senior research scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES).
"And it could lead to even more sea-level rise, up to 10 feet [3 m], if it draws the surrounding glaciers with it," Scambos said in a statement, referring to the weakening effect one ice shelf collapse can have on other nearby glaciers.
Because Thwaites is changing so quickly and could significantly affect global sea-level rise, more than 100 scientists in the United States and the United Kingdom are collaborating on eight research projects to observe the glacier from top to bottom; results from several of those teams were presented at AGU.
Scambos said at the briefing. "We've got a few more years to go to assemble further results and integrate them, so we have a better understanding of this glacier moving forward."
Melt from below
At Thwaites, scientists bored holes through the ice to peer at the ocean hundreds of meters underneath, and other researchers deployed remote-controlled diving robots to study the glacier's grounding zone. They took temperature readings and measured salinity in the ocean, confirming that waters deep under the ice were warm enough to cause significant melt.
Another group of scientists found that tidal activity could interact with the ice overhead to actively pump warm water farther inland through channels that were already carved by melt, thereby accelerating Thwaites' deterioration, said presenter Lizzy Clyne, an adjunct professor at Lewis and Clark College in Portland, Oregon.
"When you have low tide, the floating ice shelf portion sinks down," Clyne said at AGU. "This acts kind of like a lever, and can actually pull up a section a little bit inland that can pull water in. And then the opposite happens when you have high tide and the water level rises — the floating section rises up." This up-and-down movement, known as tidal pumping, pulls water farther inland and weakens even more of the glacier, Clyne explained.
"Hundreds of icebergs"
Once-solid ice masses on Thwaites that formerly helped to hold the ice shelf together are also breaking down; the glacier's icy "tongue" — a part of the ice shelf that protrudes seaward — on the western side is now "just a loose cluster of icebergs and no longer influences this eastern, more stable section of the ice shelf," according to AGU presenter Erin Pettit, an associate professor of geophysics and glaciology at Oregon State University. When the tongue was more solid, it slowed the flow of the eastern ice shelf toward the ocean. But with the loss of that resistance, the flow of the eastern shelf has shifted over the past 10 years. Cracks are rapidly spreading through the ice, and that portion of the shelf will likely shatter "into hundreds of icebergs" within just a few years, Pettit said.
The effect would be somewhat like that of a car window "where you have a few cracks that are slowly propagating, and then suddenly you go over a bump in your car and the whole thing just starts to shatter in every direction," she said.
While the immediate prognosis is grim for Thwaites' ice shelf, the longterm forecast for the rest of the glacier is less certain. Should the shelf collapse, the glacier's flow will likely accelerate in its rush toward the ocean, with parts of it potentially tripling in speed; other chain reactions could also play a part in driving accelerated ice fracturing and melt, Scambos said at AGU. But the timeframe for those changes will be decades rather than a handful of years, according to the briefing.
Meanwhile the ITGC teams will continue to monitor and analyze changes in the ongoing interplay between glacier, ice shelf and ocean on Thwaites, to help world leaders and policy makers prepare for what comes next.
Manchester City cruise to win while neighbors United sack Solskjaer******
LONDON, Nov. 21 (Xinhua) -- Manchester City claimed an easy win at home to Everton on Sunday to keep in the race for the Premier League title along with Chelsea and Liverpool.。
Although Pep Guardiola's side lost Kevin de Bruyne to Covid-19 in the days before the game, they were clear winners on Sunday, opening the scoring in the 44th minute through Raheem Sterling, who beat Jorden Pickford after a magnificent defense-splitting pass from Joao Cancelo.。
Rodri doubled City's lead with a thundering shot in the 55th minute and Bernardo Silva added a third from close range four minutes from time.。
Tottenham beat Leeds United 2-1 in Antonio Conte's home debut in the Premier League thanks to goals from Pierre-Emile Hojbjerg and Sergio Reguilon, whose second-half strikes overturned Daniel James's 44th-minute opener for Leeds which had threatened to make things difficult for the home side.。
On Saturday Chelsea win 3-0 away to Leicester City to ensure they remain top of the league, while Liverpool demolished Arsenal 4-0 to stay second and West Ham were beaten 1-0 away to Wolves.。
Meanwhile Manchester United's 4-1 defeat to Watford led to Ole Gunnar Solskjaer being sacked as first-team coach on Sunday lunchtime with former player Michael Carrick taking over on a short-term basis. Enditem。