Skyscraper-Size Ice Structures Discovered Beneath Greenland Ice Sheet
Beneath the barren whiteness of Greenland, a mysterious world has popped into view. Using ice-penetrating radar, researchers have discovered ragged blocks of ice as tall as city skyscrapers and as wide as the island of Manhattan at the very bottom of the ice sheet, apparently formed as water beneath the ice refreezes and warps the surrounding ice upwards.
The newly revealed forms may help scientists understand more about how ice sheets behave and how they will respond to a warming climate. The results are published in the latest issue of Nature Geoscience.
“We see more of these features where the ice sheet starts to go fast,” said the study’s lead author, Robin Bell, a geophysicist at Columbia University’s Lamont-Doherty Earth Observatory. “We think the refreezing process uplifts, distorts and warms the ice above, making it softer and easier to flow.”
The structures cover about a tenth of northern Greenland, the researchers estimate, becoming bigger and more common as the ice sheet narrows into ice streams, or glaciers, headed for the sea. As meltwater at the bottom refreezes over hundreds to thousands of years, the researchers believe it radiates heat into the surrounding ice sheet, making it pick up its pace as the ice becomes softer and flows more easily.
Since the 1970s, and as recently as 1998, researchers flying over the region mistook radar images of these structures for hills. Newer instruments flown during NASA’s IceBridge campaign to map ice loss at both poles found the hills to be made of ice instead of rock. Bell, who had discovered similar ice features at the base of the East Antarctic ice sheet, recognized them immediately.
While mapping Antarctica’s ice-covered Gamburtsev Mountains in 2008 and 2009, Bell and colleagues discovered extensive melting and refreezing along ridges and steep valley walls of the range. Though researchers had long known that pressure and friction can melt the bottom of ice sheets, no one knew that refreezing water could deform the layer-cake structure above. In a 2011 study in Science, Bell and colleagues proposed that ice sheets can grow from the bottom up, not just from the top-down accumulation of falling snow.
The current study builds on the findings from Antarctica by linking the bottom features to faster ice sheet flow. The researchers looked at Petermann Glacier in the north of Greenland, which made headlines in 2010 when a 100-square mile chunk of ice slipped into the sea. They discovered that Petermann Glacier is sweeping a dozen large features with it toward the coast as it funnels off the ice sheet; one feature sits where satellite data has shown part of the glacier racing twice as fast as nearby ice. The researchers suggest that the refreeze process is influencing the glacier’s advance hundreds of miles from where Petermann floats onto the sea.
“Overall, these observations suggest that basal freeze-on is a key control on the large-scale flow of Petermann Glacier, a possibility that has not been explored previously,” writes University of Texas researcher Joseph MacGregor in the same issue of Nature Geoscience.
Greenland’s glaciers appear to be moving more rapidly toward the sea as climate warms but it remains unclear how the refreeze process will influence this trend, the researchers said.
They expected to find bottom features in the ice sheet’s interior, as they did in Antarctica, but did not expect to see features at the edges, where lakes form and rivers flow over the surface, they said. Water from those lakes and rivers appears to fall through crevasses and other holes in the ice to reach the base of the ice sheet, where some of it apparently refreezes. Their discovery indicates that refreezing and deformation at the base of the ice sheet may be far more widespread than previously thought. Bell and her colleagues believe that similar features may come to light as other parts of Greenland and Antarctica are studied in closer detail.
Flying over northern Greenland during the 2011 Ice Bridge season, Kirsty Tinto, a geophysicist at Lamont-Doherty, sat up straight when the radar images began to reveal a deformed layer-cake structure. “When you’re flying over this flat, white landscape people almost fall asleep it’s so boring—layer cake, layer cake, layer cake,” said Tinto, a study coauthor. “But then suddenly these things appear on the screen. It’s very exciting. You get a sense of these invisible processes happening underneath.”
The study was funded by the U.S. National Science Foundation and NASA. Other authors: Indrani Das, Michael Wolovick, Winnie Chu, Timothy Creyts, Nicholas Frearson, Abdulhakim Abdi, all of Lamont-Doherty, and John Paden of University of Kansas.
By Ilana Cohen
Four years ago, Jacob Abel cast his first presidential vote for Donald Trump. As a young conservative from Concord, North Carolina, the choice felt natural.
But this November, he plans to cast a "protest vote" for a write-in candidate or abstain from casting a ballot for president. A determining factor in his 180-degree turn? Climate change.
Fractures Among Young Climate Conservatives<p>While young conservatives have united around the urgency of climate change, they remain divided over how to bring their concerns to the ballot box. Some embrace right-wing <a href="https://www.washingtonpost.com/politics/biden-attacks-republican-convention/2020/08/24/434e5b46-e66d-11ea-970a-64c73a1c2392_story.html" target="_blank">attacks</a> painting Biden as a "tool of the left" and find his climate agenda "radical." Others can't find a way to justify voting for Trump, even if it means breaking with their party.</p><p>Patrick Mann from Orange County, California, voted for Trump in 2016. But today, he's leading Aggies for Joe at Texas A&M University and is co-founder of Texas Students for Biden. </p><p>Mann grew up watching wildfires ravage his home state, nearly forcing his family to evacuate in 2017. The GOP is failing to "meet the moment" for climate action, Mann said. He's hoping Biden will deliver on a promise to "<a href="https://www.desmoinesregister.com/story/opinion/columnists/caucus/2020/01/06/joe-biden-democrat-president-iowa-caucus-restore-soul-our-nation/2806422001/" target="_blank">restore the soul of our nation</a>." </p><p>Taylor Walker from Pensacola, Florida, is also determined to make her voice heard on climate, including by casting her first-ever vote for president—but not for Biden.</p>
A False Equivalency<p>Young climate conservatives may fear climate denial and delayed climate action, but more than that, they fear the growing political momentum around the Green New Deal, the massive spending it entails and <a href="https://joebiden.com/climate-plan/" target="_blank">Biden's citing of it</a> as a "crucial framing for meeting the climate challenges we face."</p><p>Many don't want to split with their party to support a Democrat whose <a href="https://www.npr.org/2019/09/03/757220130/joe-biden-on-bipartisanship-gun-control-and-regrets-over-inaction-after-a-traged" target="_blank">allegedly bipartisan intentions</a> they doubt. If stymieing what they consider a radical green agenda means re-electing a climate change denying president, so be it. </p><p>"I'm scared of climate change, but I'm also scared of the Green New Deal and what it means for America," said Ben Mutolo, a republicEN spokesperson and junior at SUNY College of Environmental Science and Forestry. </p><p>Mutolo felt encouraged by former Ohio Governor John Kasich's <a href="https://www.rollcall.com/2020/08/17/kasich-speech-to-democratic-convention-follows-years-of-building-conservative-credentials/" target="_blank" rel="noopener noreferrer">appearance</a> at the Democratic National Convention, but he still struggles to see himself voting for Biden. Though the candidate paints himself as a <a href="https://www.latimes.com/politics/story/2020-08-12/harris-biden-different-generation-similar-political-instinct" target="_blank" rel="noopener noreferrer">centrist,</a> Mutolo believes he's "cozying up to the ultra-progressive left." </p><p>Mutolo, who wants to see market-based climate solutions like a carbon tax, feels torn between a candidate whose climate plan relies on taking an "<a href="https://joebiden.com/environmental-justice-plan/#" target="_blank" rel="noopener noreferrer">All-of-Government approach</a>," and one with no efforts to reign in global warming at all. <span></span></p><p>Leiserowitz said he appreciated how a conservative might feel Biden's climate plan "doesn't jive with their limited government, free-market approach."</p><p>But he sees a strong distinction between voting for a presidential candidate with a <a href="https://www.nytimes.com/2020/07/14/us/politics/biden-climate-plan.html" target="_blank">$2 trillion climate plan</a> that includes large renewable energy investments, which have <a href="https://climatecommunication.yale.edu/publications/politics-global-warming-april-2020/" target="_blank" rel="noopener noreferrer">bipartisan support</a>, and a candidate trying "to take the country in the opposite direction, towards more fossil fuels."</p>
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Toxins in water produced by cyanobacteria was likely responsible for more than 300 elephant deaths in Botswana this year, the country's wildlife department announced on Monday.
How Did Cyanobacteria Poison the Elephants?<p>Cyanobacteria are microscopic organisms common in water and sometimes found in soil. Some cyanobacteria produce neurotoxins.</p><p>The cyanobacteria "was growing in pans" or watering holes, the principal veterinary officer of the Department of Wildlife and National Parks, Mmadi Reuben, told reporters.</p><p>Reuben said the deaths had "stopped towards the end of June 2020, coinciding with the drying of pans."</p><p>"However we have many questions still to be answered such as why the elephants only and why that area only? We have a number of hypotheses we are investigating," added Reuben.</p><p>Similar elephant deaths have also been recorded in neighboring Zimbabwe.</p>
Climate Change to Blame?<p>Not all cyanobacteria are toxic but scientists say varieties dangerous to humans and animals are occurring more frequently as climate change drives up global temperatures.</p><p>Southern Africa's temperatures are rising at twice the global average, according to the Intergovernmental Panel on Climate Change.</p>
Elephant Paradise?<p>Africa's overall elephant population is declining due to poaching. But Botswana, home to almost a third of the continent's elephants, has seen numbers grow to around 130,000.</p><p>Botswana's government said it was continuing studies into the occurrence of the deadly bacteria. In the winter, elephants hydrate themselves mainly by eating roots and bark, especially of the baobab tree.</p>
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