“We're living in a time when, even in the last few years, we have seen extreme weather events become even more and more common,” says Golledge. That number is similar to what the IPCC projected for the “worst case scenario” in their last comprehensive report in 2013, predicting about nine inches of sea level rise from Greenland and Antarctica. But the most drastic impacts of sea-level rise, they say, are likely to kick in only after the turn of the century, giving communities around the world more time to adapt. Now, a team has unraveled evidence of that human influence. But about a century ago, pieces of it started to retreat in measurable ways. (See what the world would look like if all the ice melted.). ... and thinning has spread across 24% of West Antarctica since 1992. In 2014, this iceberg, 20 miles wide, broke off the tongue of the glacier and floated away. “The question was, this hasn't been observed in Antarctica, and certainly not on such a scale,” says Frank Pattyn, a glaciologist at the Free University of Brussels in Belgium who was not involved in the study. Antarctica is losing ice at an accelerating rate. In modern times, Antarctica still holds surprises. Keeping future greenhouse gas emissions in check would go a long way toward keeping those crucial winds from weakening further, the water under the edge of the ice chilly, and the ice frozen. When they do, more warm water ends up near the edge of the ice sheet, which means more ice melts away. To answer these questions, scientists had to develop computer simulations that mimicked the ways the ice sheets behave. But if MICI were triggered there, the authors suggested, the collapse of some major glaciers, like Thwaites or Pine Island in West Antarctica, could ensue rapidly and irreversibly, committing the oceans to an extra nine feet of water over the coming centuries. But scientists are throwing their weight into solving the question. In the past decade, we learned how much faster ice, like this glacier in South Shetland Islands, Antarctica, is melting due to climate change. Stunning drone footage shows how an iceberg the size of Houston, Texas is holding on by a thread. But a warming planet has very clearly changed the way winds move around Antarctica—and that change is likely to continue, unless something drastic happens to slow or reverse the warming process. Those edges are “buttressed,” or supported, by long tongues of ice shelves, which help keep the ice behind them stable. East Antarctica is much higher in elevation than West Antarctica. The impacts are already leaking out of the poles. Does MICI exist? Oceans have already risen more than 8 inches since 1880, and between 1992 and 2017, Antarctica lost 2.71 trillion metric tons of ice. Updated 1320 GMT (2120 HKT) May 16, 2019 . Antarctica is expected to respond slowly to underside melt at first, with an accelerating response later in the century. “[West Antarctic Ice Sheet] melting will affect everyone,” says Steig. Warming waters caused by climate change will continue to accelerate the melting of ice around the world. Aug 12, 2019 . Sat 28 Dec 2019 02.00 EST. The continent of Antarctica has been losing more than 100 cubic kilometers (24 cubic miles) of ice per year since 2002. January 31, 2019 / 12:23 PM / CBS News Polar vortex may be linked to climate change Researchers say a massive cavity the size of two-thirds of Manhattan was found under a glacier in Antarctica. In the past, and even up to the early part of the record the scientists looked at in the 1920s, ice melted during warm phases and grew back during cold phases. If the world continues to burn greenhouse gases unabated, following the worst-case scenario, the authors predict that the two ice sheets will add about 10 inches to the world’s oceans by 2100. “What happens in the Antarctic does not stay in the Antarctic, and that’s what they show very clearly,” says Pattyn. MAR forced by GFS suggests that the highest melt extent over Antarctica in the modern area (>1979) has been reached on 24-Dec-2019 with ~15%. By Stephanie Pappas 16 January 2019. The shifting winds and warm ocean phases have eaten away at the ice more quickly than it’s being replaced. They tested whether their models matched up with what we knew about how the ice sheets melted and how high sea levels rose at those times in the past. LOGIN Subscription Offers. Pine Island Glacier, in West Antarctica, is retreating quickly. But the patterns in this region match up nearly perfectly with conditions far away, in the tropical Pacific Ocean, where much better, longer-term records exist—so the team could extrapolate how the polar-region winds have changed over the last century. Over decades, the temperature of the water has waxed and waned, driven in part by natural climate cycles that send different water masses close to the edge of the ice sheet at different times, cycling through from cold to a little less cold every five years or so. By Alex Fox Jan. 14, 2019 , 3:30 PM. ... Now that ice is melting at an accelerating rate, in part because of climate change. Changes in the ice sheets, they found, could influence global climate profoundly—slowing down major ocean circulation pathways, skewing air temperatures around the world, and somewhat surprisingly, making climate more variable from year to year. Take Saunders … Heat Flow in Southern Australia and Connections With East Antarctica, Geochemistry, Geophysics, Geosystems (2019).DOI: 10.1029/2019GC008418 Sometimes, those winds have weakened or reversed, which in turn causes changes in the ocean water that laps up against the ice in a way that caused the glaciers to melt. In a separate analysis, the team led by Golledge found that their ice sheet model could match the modern and Last Interglacial records well—also without MICI. “If sufficient warming occurs to remove the ice shelf of Thwaites Glacier in West Antarctica, and to drive retreat into the deep basins, the calving cliff could be much higher and wider than at Jakobshavn, generating higher stresses, which would be expected to drive faster fracture based on well-understood physical principles,” he wrote, “leav[ing] the real chance of retreat beyond some threshold becoming very rapid.”, Most dire projection of sea-level rise is a little less likely, reports say, See the Huge Crack in West Antarctica Before Iceberg Broke Off. Glacial melting in Antarctica may become irreversible ... Last modified on Tue 9 Jul 2019 07.07 EDT. Updated 8:24 PM ET, Mon January 14, 2019 . But now the glaciers and ice shelves in this frigid region are showing signs of melting, a development that portends dramatic rises in sea levels this century and beyond. Melting from Greenland and Antarctica would not only bump up sea levels but might bring more extreme weather and dramatic shifts in temperature, according to a study published in Nature in February. And we certainly should not rule it out, says Alley. Once she could tell that the results from the model matched up with data describing the past and present, she could be more confident that it would forecast the future well. “The sea-level estimates maybe aren’t as bad as we thought, but the climate predictions are worse,” says Golledge. The towering glaciers of West Antarctica hold the fate of the world’s coasts in their flanks. They used a suite of climate models to look at how the wind patterns would have evolved over the last 100 years if human-caused global warming weren’t in play, and compared that with what the winds actually did. A buttressing ice shelf melted away, leaving the glacier behind it to retreat even more rapidly, ‘“unzipping” into the ice sheet,” Richard Alley, a climate scientist from Penn State who was not involved in the study wrote in an email. Was it possible that it could influence the vast glaciers of West Antarctica, some of which were at least ten times bigger than Jakobshaven? “The holy grail is to find a law that would apply to every single glacier in Greenland and Antarctica that would capture the way that glaciers calve and transform,” says Morlighem. “It was very hard to imagine that the ice sat around happily for millennia and then decided to retreat naturally just as humans started perturbing the system, but the evidence for forcing by natural variability was strong,” writes Richard Alley, a climate scientist at Pennsylvania State University, in an email. Antarctica’s Larsen C Ice Shelf experienced its highest rate of melting since records began 40 years ago from 2019-2020, a new study has found. It’s still not clear, says Matthieu Morlighem, a cryosphere scientist at the University of California, Irvine, who was not involved in the studies. The glaciers have been receding because their snouts spill over the edge of the continent into the surrounding ocean, which is warmer than the ice. (Read about the "tipping point" here). The glacier ice is attached the “rim” of the bowl, but if it melts back past that edge, warm ocean water can spill underneath it and melt it even more quickly from the bottom. The ground underneath them, it turns out, is concave, like a bowl. West Antarctica is melting faster than expected, here’s why that’s bad https://bit.ly/2JUKcxq By Marshall Connolly (CALIFORNIA … The Russian navy, for example, has spotted five in total since October 2019. How much will sea levels rise? JUST WATCHED American first person to cross Antarctica solo. What was extra shocking was just how fast the ice could retreat under this runaway scenario, leading to about three feet of sea level rise fed from Antarctica alone by 2100—much faster than previous estimates, which generally proposed increases of only a few centimeters by the end of the century. That is in no way a get-out-of-jail-free card, say the authors of both studies. In a study published Monday in Nature Geoscience, a team of scientists showed that over the past century, human-driven global warming has changed the character of the winds that blow over the ocean near some of the most fragile glaciers in West Antarctica. Today’s pattern—with about equal west-flowing and east-flowing winds—means the whole region ends up quite a bit warmer than it was 100 years ago, when the wind flowed toward the west most of the time. Many ice sheets in both Greenland and Antarctica stretch out into the sea around them, like the cap of a mushroom floating on top of the water below. Known as East Antarctica, this section has an average al… Antarctic ice melt and climate change will contribute to rising sea levels around the globe over the next 150 years. Aug 12, 2019 ... More Emissions, Faster Melting. One new paper 1, which states there has been less surface melting recently than in past years, has been cited as “proof” that there’s no global warming.Other evidence that the amount of sea ice around Antarctica … But now, because of the slow warming of the planet, the whole baseline has moved up. For years, scientists have watched and learned that those glaciers are crumbling and melting, the rate speeding up over the decades and imperiling the stability of the entire ice sheet. There has been lots of talk lately about Antarctica and whether or not the continent’s giant ice sheet is melting. In her office amidst the snowy peaks of Grenoble, France, where she was visiting, she started to work through the model, using statistics to dig into the details of how the different pieces of physics might influence the overall shape, size, and behavior of the ice sheets—both in the past, at those hot points in Earth’s climate history, and in the modern world, where satellite data could tell her precisely where the ice sheets were melting most. PUBLISHED February 6, 2019. The ultimate cause of the wind patterns, they found, is human-caused climate change. But over the last century, that balance has come undone. (See what the world would look like if all the ice melted away). A 2019 study led by Nicholas Golledge stated that warm-ocean-driven melt from Antarctica and Greenland combined could contribute up to 10 inches to global sea level by the year 2100. Replay. Golledge and his colleagues also attached their ice sheet model to a global climate model, in order to see how the impacts of ice melting at the poles would influence climate and oceans in farflung parts of the world (in the past, ice sheet models have traditionally been run separately, primarily because computers haven’t been powerful enough to link them together). New analysis of Antarctica's melting glaciers refines our understanding of climate change, while risks of global impacts remain significant. East Antarctica’s ice is melting at an unexpectedly rapid clip, new study suggests. More information: Alicia Pollett et al. Scientists link climate change to melting in West Antarctica Aug 13, 2019 Researchers explore how Antarctic ice sheets will respond to climate change and global sea level rise A new study found that Antarctica is losing six times more ice each year than it was 40 years ago. And when she and her colleagues looked at what the MICI-less versions of the model predicted would happen to the ice sheet in the future, they found that sea-level rise ramped up significantly in the 2060-2070 decade, but hit not more than about 16 inches under the IPCC’s RCP 8.5 scenario (commonly referred to as the “worst case” scenario). These numbers were bigger and coming sooner than most of the previous estimates. If it were all to melt, it would raise sea levels by 190 feet. A new study helps solve the puzzle of why the continent’s western glaciers are melting so fast A rare lava lake. Nov 12, 2019 . Not any more. They used that model to predict how the Greenland and Antarctic ice sheets will speed up their melting in the coming decades. At a Glance. Remember when sea ice in Antarctica was increasing? She found that when she “turned off” the MICI part of the model, she could still find answers that matched up with those past and present reconstructions of the ice sheet. 2020 National Geographic Partners, LLC. Read about how one ice shelf on the Antarctic Peninsula may be the first of many to collapse. Nov 12, 2019 ... "Today, only the most intense atmospheric rivers trigger melting, but under the warming projected for Antarctica by 2100, rare melt events would become commonplace. The answers will reverberate far beyond the scientific community. But Antarctica is a complicated place that changes a lot because of natural variability, so it has been challenging to pinpoint the extent of human influence on the changes. If residents of Palau are going to have an extra three feet of water sloshing at their doorstep by 2100, they need to know sooner rather than later. That doesn’t mean that MICI doesn’t exist, she says. So across the scientific community, researchers started asking: Was MICI real? July 13, 2017 - A giant iceberg the size of Delaware has broken off the Larsen C Ice Shelf in West Antarctica. Sometimes, those winds—cousins of the famous raging band of Southern Ocean winds known as the Roaring 40s—slacken or even reverse. And that could be devastating for the ice. All rights reserved. The newly independent iceberg is one of the largest ever recorded. Earth's Tilt May Exacerbate a Melting Antarctic. Tamsin Edwards, a climate scientist at Kings College in London, read the original paper and immediately wondered whether she could use careful, sophisticated math to better pin down the likelihood of MICI occurring. The warm water melts away the ice. This process—called “MICI,” for “marine ice cliff instability”—seems to be underway at the Jakobshaven glacier in Greenland. More and more evidence emerges every year showing that the Greenland and Antarctic ice sheets are getting smaller. Other chunks of ice continue to shear off the glacier. Scientists knew that the strength of the winds in this region of the Amundsen Sea affected the water temperature. But if things are just unpredictable and extremely variable from year to year—well, that’s a much harder problem for society to solve.”. The study goes on to say that sea levels cannot be rising because of glaciers melting in Antarctica because its actually gaining ice. © 1996-2015 National Geographic Society, © 2015- Wed, Nov 25, 2020. That’s well within the time frame when carbon dioxide and other greenhouse gases had started to accumulate thickly in the atmosphere, so it seemed logical to think that human influence was affecting the ice. “If we carry this pattern forward, we may move to a situation where we’re flipping between warm and very warm,” says Holland. That’s not likely to happen anytime particularly soon, scientists think, but some parts of the ice sheet are particularly vulnerable, in danger of crossing a crucial “tipping point” if they retreat too far. “Dealing with steady warming is easier, in many ways. New research takes into account how atmospheric temperatures in Antarctica will cause more ice melt and sea level rise than ocean warming. (See what a 10 billion ton chunk of ice looks like in this video). “We were all asking, can such a mechanism be scaled to the bigger place?”. Melt extent (ME, the extent of the area subject to melting) in 2008 set a new minimum with 297,500 square kilometers, against an average value of approximately 861,812 square kilometers.” This evidence suggests that Antarctica, where 90% of the land based ice in the world resides, is increasing in mass. Compared to the Arctic, Antarctic sea ice shows less variability in summer, and more variability in winter. To check whether they were working right, scientists would compare their models to real observations. This February heatwave was the third major melt event of the 2019-2020 summer, following warm spells in November 2019 and January 2020. All rights reserved. Instead of the cycle flipping between cold and very cold, the flip is between warm and cold. West Antarctica is melting—and it’s our fault. “The effects will be global, because sea level will rise globally.”, Photograph by Jeff Schmaltz, NASA/GSFC/MODIS Land Rapid Response Team, West Antarctica is melting—and it’s our fault, See the crack splitting an Antarctic ice shelf in two. © 1996-2015 National Geographic Society, © 2015- Pine Island Glacier and Thwaites Glaciers, for example, are losing about 100 billion tons of ice each year, and more in bad years. The Antarctic ice sheet sat more or less stable in shape and size for many thousands of years. The towering glaciers of West Antarctica hold the fate of the world’s coasts in their flanks. So scientists looked to the past, to periods like the Pliocene, about 3.4 million years ago, or the Last Interglacial, about 120 thousand years ago—periods when the planet was as warm or warmer than today. “It’s more significant that these events are coming more frequently.“ But it does mean that there’s a lot more work to be done to understand how, why, and maybe when it might kick in. Those glaciers are particularly sensitive to melting at their snouts. But only recently have satellites been launched into space that could precisely weigh the ice sheet from afar, giving a concrete sense of how much ice is sloughing off. In 1974, one of these strong moments of melting pushed the glaciers past one of these “rims,” and since then the glacier has melted much more quickly than it did before—at least 50 percent more melt after that un-groundig than before, said Eric Steig, an atmospheic and ice core scientist at the University of Washington and an author of the paper. “So in the old days, it was cold all the time—it flopped between cold and very cold.”. If it all melted away, global sea levels would rise by about 10 feet or more. Their collapse could send sea levels up by at least a foot by 2100—and potentially much more. Several particularly notable moments of wind-flipping, like in the 1970s, matched up closely with major retreats of the Pine Island and Thwaites glaciers. “If you think about this one event in February, it isn’t that significant,” said Pelto. But if those ice shelves are lost, they can leave in their wake tall cliffs towering over the ocean or rock below. (Read about how one ice shelf on the Antarctic Peninsula may be the first of many to collapse). What’s more, changes to the ice sheets in both Greenland and Antarctica could also trigger planet-wide shifts in temperature, ocean circulation, and many other parts of the climate system, says says Nick Golledge, a climate scientist at the Antarctic Research Center of the University of Victoria, Wellington, and the lead author of one of the studies. West Antarctica is about as big as the contiguous western United States and covered with ice that's over a mile thick in places. But while the science was clear that human influences on climate would affect the ice down the line, it has been hard to tell whether human-driven global warming has affected the melting already underway. The idea was simple: Ice is a material, like steel or wood, that can stand only so much stress before it bends or breaks. But the future isn’t yet written, Steig stressed. It is smaller than the number predicted by the 2016 study, which said that Antarctica alone might feed more than three feet of sea level rise into the oceans by 2100. Larger Image Two-thirds of Antarctica is a high, cold desert. PUBLISHED August 12, 2019. Both studies revise the estimates of just how much sea levels will rise by 2100 downward, suggesting that Antarctica could contribute somewhere between about three to 16 inches to the world’s oceans under the “worst case” scenarios. In the past decades, some glaciers in the region have been retreating shockingly quickly. Larger Image The Antarctic ice sheet. https://www.nationalgeographic.com/environment/2019/02/antarctic-greenland-ice-melt-less-bad.html, See what the world would look like if all the ice melted. But the holy grail questions for scientists and communities everywhere concern their future: How much smaller will they get, and how fast will they shrink? These changes largely result from the geographic differenc… The sea level rise estimates may be lower, but the overall picture of how melting ice sheets will affect climate is grim. MICI hasn’t yet been observed in Antarctica, where there are much larger glaciers. Antarctic glaciers lost around 40 billion tons of ice melt each year from 1979 to 1989. It’s not exactly news that Greenland and Antarctica are shedding ice at record rates. Glacial melting in Antarctica may become irreversible. https://www.nationalgeographic.com/environment/2019/08/west-antarctic-glaciers-melting-human-influence.html, See what a 10 billion ton chunk of ice looks like in this video, See what the world would look like if all the ice melted away. The frozen continent of Antarctica contains the vast majority of all freshwater on Earth. “In the 1920s, the winds were pretty much consistently blowing toward the west,” says Holland. The main thing that controls whether warm water makes it to the edge of the ice sheet, it turns out, is the strength of the winds a little bit farther offshore, in the heart of the icy, bitter Amundsen Sea. The Reason Antarctica Is Melting: Shifting Winds, Driven by Global Warming. “We now have evidence to support that human activities have influenced the sea level rise we’ve seen from West Antarctica,” says lead author Paul Holland, a polar scientist at the British Antarctic Survey. And if those cliffs are tall—over about 300 feet—the ice behind will fail, shearing off in enormous blocks. Upside-down “rivers” are melting ice shelves in Antarctica from beneath, according to a new study. Sea ice waxes and wanes with the seasons, but minimum and maximum extents rarely match from year to year; over years and decades, summer and winter extents vary. Warm water soaking the base of the ice sheets, they found, was enough to force key parts of the ice sheet to melt away. Just how warm the ocean is, though, matters a lot. The massive West Antarctic ice sheet holds something like 6 percent of the world’s fresh water frozen in its guts. East Antarctica is the coldest spot on earth, long thought to be untouched by warming. This footage from February 2017 shows a major rift in the ice shelf before the iceberg broke free. These data go back only a few decades—barely a blink of Earth’s eye. One study, led by researchers from the University of Massachusetts, Amherst and Penn State, found that the ice sheets in their models could only match that data from the past if they included a mechanism called the “marine ice cliff instability.”. Antarctica ice melt has accelerated by 280% in the last 4 decades. Adding that to the other components that make up sea level rise—how the ocean expands as it warms (which will likely add about 10 inches), the melt from mountain glaciers (about six inches), and changes to the amount of water stored in lakes and rivers on land (one and a half inches), and the total is still a daunting number somewhere between just under two- to over three- foot range. But in 2016, an eyebrow-raising idea ricocheted through the scientific community: It was possible, the authors said, that a warmer planet could push the towering ice cliffs at the fringes of the Antarctic ice sheet to essentially self-destruct, collapsing like a set of dominoes. The extra greenhouse gases humans have pumped into the atmosphere over the past few hundred years have changed the way heat moves around the planet so thoroughly that they’ve changed the shape of the basic wind patterns at the poles. But two new pieces of research, published Wednesday in Nature, suggest a more measured retreat is likely in the coming decades. Click here to read The Larsen C Ice Shelf Collapse Is Just the Beginning—Antarctica Is Melting. 2020 National Geographic Partners, LLC. It’s still an enormous amount of extra water that could slosh up onto coasts, enough to debilitate cities from Boston to Shanghai. Records of wind strength and direction only went back until 1979.
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