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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.
US teen Kyle Rittenhouse cleared over protester deaths******
Kyle Rittenhouse (left) collapses to his chair and cries as he is found not guilty on all counts at the Kenosha County Courthouse on November 19, 2021, in Kenosha, Wisconsin.
Kyle Rittenhouse, the American teenager who shot dead two men during protests and riots against police brutality in Wisconsin last year, was acquitted of all charges on Friday after a high-profile and politically divisive trial.
A jury found Rittenhouse, 18, not guilty of reckless and intentional homicide and other charges stemming from the shootings that took place in August 2020 in Kenosha, Wisconsin.
Rittenhouse, who claimed he acted in self-defense, sobbed and shook as the verdict was read, sank into his chair and embraced his lawyer before rushing out of the courtroom.
President Joe Biden warned against violence following the verdict in the closely watched trial and appealed for calm.
"While the verdict in Kenosha will leave many Americans feeling angry and concerned, myself included, we must acknowledge that the jury has spoken," Biden said in a statement. "I urge everyone to express their views peacefully, consistent with the rule of law."
There were scattered cheers and clapping from supporters of Rittenhouse outside the Kenosha courthouse after the verdict.
Several opponents marched around beating drums and chanting "Guilty, guilty, the whole system is guilty as hell."
Rittenhouse testified during the two-week trial that he shot dead two men and wounded another with his AR-15 semi-automatic rifle after being attacked.
Prosecutors dismissed the self-defense claim, saying it was the then 17-year-old Rittenhouse who "provoked" the events during a night of unrest in Kenosha.
Rittenhouse faced five charges – one count of intentional homicide, one count of reckless homicide, one count of attempted intentional homicide and two counts of recklessly endangering safety.
The most serious charge – intentional homicide – carried a mandatory sentence of life in prison.
The jury deliberated for a total of 26 hours over four days before delivering a unanimous verdict of not guilty on all counts.
The case drew national attention because it arose from the Black Lives Matter demonstrations that swept the country last year and featured a controversial mix of guns, racial tensions and vigilantism.
Civil unrest erupted in Kenosha, a city of 100,000 on the shores of Lake Michigan, in August 2020 after a white policeman shot a Black man, Jacob Blake, in the back several times during an arrest, leaving him paralyzed.
In right-wing and pro-gun circles, Rittenhouse, who claimed he went to Kenosha to protect businesses from looters and act as a medic, was hailed as a heroic figure.
Prosecutors said Rittenhouse – who lived in the neighboring state of Illinois – had come to Kenosha as a self-appointed "junior policeman" and "made a series of reckless decisions."
"Nobody deputized him," prosecutor Thomas Binger said.
A woman reacts, in anger, to the Kyle Rittenhouse verdict outside the courthouse in Kenosha, Wisconsin on November 19, 2021.
'Miscarriage of justice'
Shannon Watts, founder of gun control group Moms Demand Action, was among those denouncing the not guilty finding.
"That a teenager could travel across state lines to a protest he had nothing to do with; shoot three people, killing two; and face no criminal consequences is a miscarriage of justice and an indictment of our criminal justice system," Watts said.
New York Mayor Bill de Blasio, a Democrat, said the verdict "sends a horrible message to this country." "To call this a miscarriage of justice is an understatement," he said.
The NAACP, the African-American civil rights group, said the verdict is a "travesty and fails to deliver justice on behalf of those who lost their lives."
"A system that legitimizes vigilante murder is deeply broken," tweeted Wisconsin Representative Gwen Moore, a Democrat.
Republican lawmakers welcomed the not guilty finding.
"Justice has been served," said Wisconsin Senator Ron Johnson. "I hope everyone can accept the verdict, remain peaceful, and let the community of Kenosha heal and rebuild."
Former president Donald Trump, in a statement released on the Twitter account of his chief spokeswoman Liz Harrington, said: "Congratulations to Kyle Rittenhouse for being found INNOCENT of all charges. It"s called being found NOT GUILTY – And by the way, if that's not self defense, nothing is!"
Wisconsin Governor Tony Evers has put 500 members of the state National Guard on standby in the event of trouble.
In his statement, Biden said he had spoken to Evers and offered assistance if needed to ensure public safety.
Brianna Nelson, 37, a member of an advocacy group that works to deescalate tense situations, told AFP outside the court she was disappointed but not surprised by the verdict.
"It's a time for unity in the community," Nelson said. "It's an educational moment for both sides. We don't have to agree but we have to live together peacefully."
Speaking to reporters after the verdict, Rittenhouse's attorney, Mark Richards, said he believes his client is remorseful.
"He is in counseling for PTSD," Richards said. "He doesn't sleep at night.
"I personally don't like people carrying AR-15s around," Richards added, but "he was legal in having that firearm."
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