Sea level could rise much faster than thought, Greenland data suggest
Greenland’s largest ice sheet is thawing much faster than expected, a new study has revealed, suggesting it will add six times more water to rising sea levels than previously thought. And the trend may not be limited to Greenland, scientists worry.
The study used GPS measurements and computer modeling to estimate how much ice is lost due to: climate change of the Northeast Greenland Ice Flow (NEGIS), a prominent ice flow that drains ice and meltwater from the ice-covered interior of Greenland.
The calculations showed that the melting of NEGIS has accelerated so rapidly since 2012 that it will add more than 1.3 centimeters of water to the global ocean level by the end of this century. This is equivalent to Greenland’s total contribution to the past 50 years sea level rise.
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The NEGIS acceleration of ice melting started after the Zachariae Isstrøm glacier that protected the coastal portion of the ice flow broke off in 2012, allowing warmer seawater to penetrate deeper inland. The new data has revealed that the wave of rapid ice thinning caused by this incident propagated much deeper upstream than previously thought. Scientists were able to measure the thinning as far as 186 miles (300 kilometers) off Greenland’s northeast coast, where NEGIS meets the ocean.
“Many glaciers have accelerated and thinned near the margins in recent decades — GPS data helped us detect how far inland these near-coastal changes propagate,” study co-author Mathieu Morlighem, a professor of Earth sciences at the University of Groningen, said in a statement. Dartmouth College in New Hampshire, said in a pronunciation (opens in new tab). “If this is correct, the contribution of ice dynamics to the overall mass loss on Greenland will be greater than what current models suggest.”
Morlinghem added that similar trends may be underway in other parts of the Greenland ice sheet, as the entire system may be much more sensitive to changes in coastal areas than previously thought.
The study found that accelerating melting continued even into the winter of 2021 and summer of 2022, which were unusually cold in Greenland, suggesting the process will be quite difficult to stop.
“We can see that the entire basin is thinning and the surface speed is accelerating,” Shfaqat Abbas Khan, a researcher at the University of Denmark and lead author of the new study, said in the same statement. “Every year the glaciers we have studied have retreated further inland and we predict this will continue for decades and centuries to come. Under the current climate forcing, it’s hard to imagine how this retreat could stop.”
If confirmed, the findings will have implications for current sea-level rise forecasts, which foresee a global increase in ocean levels of 8 to 38 inches (22 to 98 cm) by the end of the century. Actual sea level rise is likely to be much greater, the authors conclude, with catastrophic consequences for residents of low-lying and coastal regions around the world.
“We foresee sweeping changes in global sea levels, more than currently projected by existing models,” Eric Rignot, a professor of Earth systems science at the University of California, Irvine, who is also a co-author of the paper, said in the statement. “Data collected in the vast interior of ice sheets, such as those described in our study, help us better represent the physical processes in numerical models and in turn provide more realistic projections of global sea level rise.”
The study was released as countries negotiate at the 27th Conference of Parties to the United Nations Framework Convention on Climate Change (COP27) in the Egyptian coastal city of Sharm el-Sheikh. The summit, building on the results of last year’s COP26 meeting on climate change in Glasgow, Scotland, will seek solutions to a wide range of climate-related emergencies, including the energy crisis and the increasing severity of extreme weather events.
The study (opens in new tab) was published Nov. 9 in the journal Nature.
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