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Human-driven climate change has led to massive ice loss in Greenland that could not be stopped even if the world stopped emitting greenhouse gases today, according to a new study published Monday.
Findings in Nature Climate Change project that 3.3 percent of the Greenland ice sheet is now inevitable to melt, equivalent to 110 trillion. tons of ice, the researchers said. This will cause nearly a foot of global sea level rise.
The predictions are more dire than other forecasts, although they use different assumptions. Although the study did not specify a time frame for the melting and sea level rise, the authors suggested much of it may occur between now and the year 2100.
“The point is that we need to plan for this ice as if it’s not in the ice sheet in the near future, a century or so from now,” said William Colgan, co-author of the study. the layer of ice on its surface with his colleagues at the Geological Survey of Denmark and Greenland, he said in a video interview.
“Each study has bigger numbers than the last. It’s always faster than expected,” Colgan said.
One reason the new research seems worse than other findings may be that it’s simpler. Try to calculate how much ice Greenland has to lose as it will recalibrate to a warmer climate. Instead, sophisticated computer simulations of how the ice sheet will behave under future global emissions scenarios. have produced less alarming predictions.
A rise of one foot global sea level would have serious consequences. If sea levels along U.S. coasts rose an average of 10 to 12 inches by 2050, a recent report from the National Oceanic and Atmospheric Administration found, the most destructive floods would occur five times more often, and moderate flooding it would be 10 times more frequent.
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Other countries — low island and developing nations such as Bangladesh – They are even more vulnerable. These nations, which have done little to fuel the higher temperatures now thawing the Greenland ice sheet, lacks the billions of dollars it will have it is necessary to adapt to the rise of the sea.
The paper’s lead author, Geological Survey of Denmark and Greenland scientist Jason Box, collaborated with scientists based at institutions in Belgium, Denmark, Finland, Norway, the Netherlands, Switzerland and the United States. to assess the extent of ice loss that is already blocked by human activity.
Just last year, the United Nations’ Intergovernmental Panel on Climate Change, which generally forecasts lower numbers of total Greenland ice loss by the end of the century, projected about half a foot of level rise of the sea from Greenland by the year 2100 in the upper part. . This scenario assumed that humans would emit a large amount of greenhouse gases for another 80 years.
The current study, on the other hand, does not account for any additional greenhouse gas emissions or specify when the melting would occur, making the comparison with the UN report imperfect.
The finding that 3.3 percent of Greenland is, in effect, already lost represents “a minimum, a lower bound,” Box said. It could be much worse than that, the study suggests, especially if the world continues to burn fossil fuels and if 2012, which set a record for Greenland ice loss, becomes more like the norm.
But this aspect of the study offers hope: Even if more sea-level rise is blocked than previously thought, reducing emissions quickly to limit warming to close to 1.5 degrees Celsius (2 .7 degrees Fahrenheit) would prevent things from getting much worse.
Greenland is the world’s largest island and is covered by an ice sheet that, if completely melted, could raise sea levels more than 20 feet. This is not in doubt, nor is the fact that in past warm periods of Earth’s history, the ice sheet was much smaller than it is today. The question has always been how much ice will thaw as temperatures rise and how quickly.
Melt rates have been increasing over the past two decades, and Greenland is the largest ice-based contributor to the rate of global sea-level rise, surpassing the contributions of both the larger Antarctic ice sheet and the mountain glaciers around the world. Greenland is in the Arctic, which is getting very warm faster than the rest of the world.
Higher temperatures in the Arctic are causing large amounts of ice on the surface of Greenland to melt. While the island’s oceanfront glaciers are also churning out huge icebergs at an accelerating rate, it’s this surface melting that’s resulting in gushing rivers of ice, disappearing lakes and giant waterfalls cascading into crevasses. the greatest losses of ice.
In the past, scientists have tried to determine what the ongoing melting of Greenland means for global sea levels using complex computer simulations. They model the ice itself, the surrounding ocean and the future climate based on different emission trajectories.
In general, the models have produced modest numbers. For example, according to the latest IPCC assessment, the most “likely” loss of Greenland by 2100 under a very high emissions scenario equates to about 5 inches of sea level rise. This represents the disappearance of 1.8 percent of the total mass of Greenland.
Most models and scenarios produce something far inferior. In a low-emissions scenario, which the world is trying to achieve right now, the IPCC report suggests that Greenland would only contribute a few centimeters to sea level rise. the end of the century.
The new research “gets numbers that are high compared to other studies,” said Sophie Nowicki, a Greenland expert at the University of Buffalo who contributed to the IPCC report. Nowicki noted, however, that one reason the number is so high is that the study considers only the past 20 years, which have seen strong warming, as the current climate to which the layer is adjusting of ice Taking a 40-year period would yield an inferior result, Nowicki said.
“This compromised number is not well known and is actually quite difficult to estimate, due to the long response time scale of the ice sheet,” Nowicki said.
Box, for his part, argues that the models on which the IPCC report is based are “like a facsimile of reality”, without enough detail to reflect how Greenland is actually changing. These computer models have sparked considerable controversy recently, with one research group charging that they do not adequately track the current high levels of Greenland ice loss.
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In Greenland, the processes that trigger the loss of ice from large glaciers often occur hundreds of meters below the sea’s surface in narrow fjords, where warm water can hit the submerged ice in complex movements. In some cases, these processes may simply be playing out at too small a scale for the models to capture.
Meanwhile, while it’s clear that the warmer air is melting the surface ice sheet, the consequences of all the water running off the ice sheet, and sometimes through and under it, pose additional questions Much of the water evaporates into cracks, called moulins, and travels along invisible paths through the ice to the sea. The extent to which this causes the ice to slip and sink forward is still up for debate and could be happening on a finer scale than the models capture.
“Individual mills, they’re not in the models,” Colgan said.
New research assesses Greenland’s future using a simpler method. Try to calculate how much ice loss from Greenland is already dictated by physics, given the current arctic climate.
An ice sheet, like an ice cube but on a much larger scale, is always in the process of melting, or growing, in response to the temperature around it. But with an ice body as large as Greenland, imagine the entire state of Alaska covered in ice one to two kilometers thick, the adjustment requires a long time This means it can be a loss almost inevitable, even if it hasn’t happened yet.
Even so, the ice sheet will leave tracks as it shrinks. As it thaws, scientists think the change will manifest itself in a place called snow line This is the dividing line between the white, high-altitude parts of the ice sheet that accumulate snow and mass even in summer, and the darker, lower-elevation parts that melt and bring water to the sea This line moves each year, depending on how hot or cool the summer is, tracking how much Greenland melts in a given period.
The new research argues that in today’s climate, the average location of the snow line must be moving inward and upward, leaving a smaller area in which ice could accumulate. This would give a smaller ice sheet.
“What they’re saying is that the climate we already have is in the process of burning off the edges of the ice,” said Ted Scambos, an ice sheet expert at the University of Colorado at Boulder who it didn’t work on paper.
Scambos, however, he said it could take well over 80 years to melt 3.3 percent of the ice sheet: the study says “most” of the change may occur by 2100.
“Much of the change they envision would occur in this century, but to achieve it [that level of retreat] it would require several centuries, perhaps more,” he said.
Future ice losses will be greater than this amount if global warming continues to progress, which it will. If the massive melting year of 2012 became the norm, for example, that would likely lead to about two and a half feet of committed sea-level rise, the study says.
Pennsylvania State University professor Richard Alley, an expert on ice sheets, said the fact that researchers still aren’t sure how the planet’s ice sheets will change and global sea levels rise demonstrates the need for more research.
“The problems are deeply challenging, will not be solved by wishful thinking, and have not yet been solved by…