The Greenland ice sheet can cause nearly a foot of sea level rise


Human-driven climate change has created massive ice losses in Greenland that cannot be stopped even if the world stops emitting greenhouse gases today, one step at a time. A new study Published on Monday.

3.3 percent of the natural climate change program findings that are now inevitable Greenland ice sheet Melting – equal to 110 trillion tons of snow, The researchers said. This would trigger a global sea level rise of about one foot.

Predictions are more dire than other predictions, although they use different assumptions. Although the study did not specify a time frame for the melting and sea-level rise, the authors suggested Most of it could be played out between now and the year 2100.

“The point is to project that ice sheet a century or so into the future as if there was no ice sheet,” study co-author William Colgan said. ice from its surface with his peers Geological Survey of Denmark and Greenland, said in a video interview.

“Each study has bigger numbers than the last. “It’s always faster than forecast,” Colgan said.

One reason new research seems worse than other findings may be that simple. Trying to calculate how much ice Greenland has to lose As it adjusts to a warmer climate. In contrast, sophisticated computer simulations of how the ice sheet would behave under future scenarios for global emissions. have made less alarming predictions.

A step up Global sea levels will have dire consequences. If sea level rise along the U.S. coast averages 10 to 12 inches by 2050, a Latest Report Invented by the National Oceanic and Atmospheric Administration, Very destructive flood Five frequent, moderate floods Often 10 times.

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In other countries Low-lying island nations and developing countries like Bangladesh – are still vulnerable. These countries, which have done nothing to fuel the high temperatures now melting Greenland’s ice sheet, Not billions of dollars Adapt to rising seas.

The paper’s lead author, Jason Box, a scientist at the Geological Survey of Denmark and Greenland, collaborated with scientists at institutions in Belgium, Denmark, Finland, Norway, the Netherlands, Switzerland and the United States. To estimate the amount of snow loss already locked in by human activities.

Last year, the UN on climate change The intergovernmental panel — which generally predicts lower figures for total ice loss from Greenland by the end of the century — planned By 2100, sea levels have risen nearly half a foot off Greenland. It was assumed that humans would release large amounts under those conditions Greenhouse gases for another 80 years.

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The current study, in contrast, does not factor in additional greenhouse gas emissions or specify when the melting will occur. The comparison with the United Nations report is imperfect.

Finding that 3.3 percent of Greenland has already been lost “represents, at the very least, a lower limit,” Box said. It could be worse than that, especially if the world continues to burn fossil fuels and if Greenland’s record-setting 2012 ice loss norm becomes the norm, the study suggests.

But that aspect of the study offers hope: Even if more sea-level rise is locked in than previously believed, cutting emissions fast enough to limit warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) could prevent things from getting too bad.

Greenland is the world’s largest island and is covered by an ice sheet that, if completely melted, could raise sea levels by more than 20 feet. There’s no doubt about it—during warmer past periods in Earth’s history, the ice sheet was much smaller than it is today. The question is always how much snow will melt — and how fast — as temperatures rise.

Melting rates have been increasing over the past two decades, and so has Greenland Largest single ice-based contributor For the rate of global sea-level rise, it exceeds the contributions of both the great Antarctic ice sheet and mountain glaciers worldwide. Greenland is in the Arctic, ie Gets very hot Faster than the rest of the world.

High Arctic temperatures will melt large amounts of ice on Greenland’s surface. This surface melting – which creates rivers of ice, disappearing lakes and giant waterfalls that disappear into crevasses – occurs when the island’s coastal glaciers shed enormous glaciers at breakneck speeds. Huge snow losses.

In the past, scientists have tried to determine what Greenland’s current melting is contributing to global sea level through complex computer simulations. They model the ice sheet, its surrounding ocean and future climate based on different emission trajectories.

In general, the models produced modest statistics. For example, According to According to a recent IPCC estimate, the “potential” loss from Greenland by 2100 under a very high emissions scenario is equivalent to about 5 inches of sea level rise. This represents the disappearance of about 1.8 percent of Greenland’s total mass.

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Most models and scenarios create something much less. In the low-emissions scenario the world is now trying to achieve, the IPCC report says Greenland would contribute only a few inches to sea-level rise. End of the century.

The new research “gets a higher number compared to other studies,” said Sophie Nowicki, an expert on Greenland at the University at Buffalo who contributed to the IPCC report. However, one reason the number is so high is that the study only looked at the past 20 years — which saw strong warming — and Nowicki observed that the ice sheet is now adjusting to the current climate. Nowicki said taking a 40-year time frame would yield less benefit.

“This definitive number is not well known and is actually very difficult to estimate because of the long response time scale of ice,” Nowicki said.

Box, for his part, argues that the models based on the IPCC report are “like a facsimile of reality” without enough detail to reflect how Greenland is actually changing. Those computer models are crazy Considerable controversy Recently, a research team is charging that they are not monitoring enough of Greenland’s current, high-volume ice loss.

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In Greenland, the processes that trigger ice loss from large glaciers often occur hundreds of meters below the sea surface in narrow fjords, where warm water can flow over submerged ice in complex motions. In some cases, these processes may play out at too small a scale for models to capture.

Meanwhile, while it’s clear that warmer air is melting the ice from the surface, the effects of all that water coming off the ice — and sometimes, through and under it — raises additional questions. Much of the water disappears into crevices called moulins and travels through the ice through invisible channels to the sea. How much ice this slick moves forward is debated and may happen at a much finer scale than the models capture.

“Individual moulins, they’re not in the samples,” Colgan said.

New research assesses Greenland’s future with a simple method. Given the current Arctic climate, it tries to calculate how much ice loss from Greenland has already been dictated by physics.

An ice cube – 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 sheet as large as Greenland — the entire state of Alaska is pictured covered in ice one to two miles thick — the adjustment is a long time. This may mean loss Although it hasn’t actually happened yet, it’s almost inevitable.

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Still, ice can leave footprints as it shrinks. When it melts, scientists think it manifests itself in what is called a transition Snow tax. It is the dividing line between the high, bright white areas of the ice sheet that accumulate snow and mass even in summer, and the dark, low-lying areas that contribute meltwater to the ocean. This line moves every year, depending on how hot or cold the summer is, tracking how much Greenland melts in a given period.

New research argues that in the current climate, the average location of the ice line should move inward and upward, leaving a small area where ice can accumulate. It will form a small ice cube.

“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, a glaciologist at the University of Colorado at Boulder. Doesn’t work on paper.

However, Scambos said It could take more than 80 years for 3.3 percent of the ice sheet to melt: “Most of the changes” could occur by 2100, the study says.

“A lot of the changes they predicted will happen in this century, but have to get [that level of retreat] It will take centuries,” he said.

Future ice losses will exceed that level if global warming continues to progress — and it will. For example, if the big melt year of 2012 is typical, it could lead to about two and a half feet of sea level rise, the study says.

Penn State University professor Richard Alley, an ice expert, said researchers are uncertain about how the planet’s ice sheets will change and how global sea levels will rise, pointing to the need for more research.

“The problems are deeply challenging, won’t be solved by wishful thinking, and have yet to be solved by business,” he said.

But Ali added that it’s clear that the more we warm the planet, the more seas will rise.

“[The] The surge may be a little lower than conventional projections, or a little higher or higher, but not too low,” Ali said.

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