Science

Future sea-level rise might be a lot larger than thought – Greenland ice loss ‘severely underestimated’

Future sea-level rise might be a lot larger than thought – Greenland ice loss ‘severely underestimated’

Meltwater river on the Zachariah Glacier, northeast Greenland

A river of meltwater on the Zachariah Glacier in northeast Greenland. Posted by Shfaqat Abbas Khan, DTU House

The brand new research mixed GPS, satellite tv for pc knowledge and numerical simulations. It has been discovered that by the tip of the century, the lack of ice from northeast Greenland might be six occasions higher than beforehand thought.

Ice continues to circulation from Greenland’s melting glaciers at an ever-increasing fee, dramatically growing world sea ranges. The brand new outcomes are printed within the journal Nature Nov. 9 present that current fashions have underestimated how a lot ice will likely be misplaced over the course of the twenty first century. Due to this fact, its contribution to sea stage rise will likely be a lot larger.

By 2100, the Northeast Greenland Ice Stream will contribute six occasions extra sea stage rise than earlier fashions predicted, including 13.5 to fifteen.5 mm (0.53 to 0.61 inches), in keeping with a brand new research. That is equal to the contribution of your entire Greenland ice sheet over the previous 50 years. Scientists from Denmark, the USA, France and Germany have been concerned within the analysis.

“Our earlier predictions of Greenland ice loss by 2100 are severely underestimated,” mentioned first writer Shfaqat Abbas Khan, professor at DTU House.

“The fashions are largely tuned to observations on the entrance of the ice sheet, which is well accessible and the place plenty of exercise seems to be occurring.”


Animation of simulated frontal positions from 2007 to 2100. A Landsat-8 picture from 2017 is used as background. Coloration signifies floor velocity. Credit score: Animation by Shfaqat Abbas Khan, DTU House, Denmark

Ice loss happens greater than 200 km inland

The analysis relies partially on knowledge collected from a community of high-precision GPS stations that attain 200 km deep into the Northeast Greenland Ice Stream, positioned behind the Nioghalvfjerdsfjord Gletscher and Zachariae Isstrøm glaciers, one of the crucial hostile and distant areas on Earth. The GPS knowledge have been mixed with floor elevation knowledge from the CryoSat-2 satellite tv for pc and high-resolution numerical simulations.

“Our knowledge present us that what we see on the entrance extends far into the ice sheet,” Hahn mentioned.

“We see that your entire basin is thinning and the floor velocity is accelerating. Every year the glaciers we studied are retreating additional inland, and we predict this can proceed for many years and centuries to return. In immediately’s local weather forcing, it’s exhausting to think about how this retreat can cease.”


Animation of simulated floor elevation change from 2007 to 2100. A Landsat-8 picture from 2017 is used as background. Colours point out modifications in floor elevation. Unfavourable values ​​imply thinning/reducing of the floor. Credit score: Animation by Shfaqat Abbas Khan, DTU House, Denmark

Important contribution to sea stage rise

In 2012, after a decade of melting, the floating extensions of Zachary-Isström collapsed, and the glacier has since retreated inland at an accelerating fee. And though the winter of 2021 and the summer time of 2022 have been significantly chilly, the glaciers proceed to retreat. As a result of northeast Greenland is a so-called arctic desert – receiving solely 25mm of precipitation per 12 months in locations – the ice sheet isn’t recovering sufficient to mitigate the melting. Nonetheless, it isn’t simple to estimate how a lot ice is misplaced and the way far within the ice sheet the method takes place. The inside of the ice sheet, which strikes at lower than one meter per 12 months, is troublesome to observe, limiting the flexibility to make correct predictions.

“It is actually wonderful that we are able to detect a refined change in velocity with high-precision GPS knowledge, which in the end, mixed with the ice circulation mannequin, informs us about how the glacier is sliding throughout its ground,” mentioned co-author Mathieu Marlighem. , Professor of Earth Sciences at Dartmouth School.

“It is attainable that what we’re discovering in northeast Greenland might be occurring in different sectors of the ice sheet. Many glaciers have been accelerating and thinning close to the sting in latest many years. The GPS knowledge helps us see how far inland this acceleration extends, probably 200-300 km from the coast. If appropriate, the contribution of ice dynamics to the entire mass lack of Greenland could be higher than present fashions counsel.’

Zachariae Isstrøm was secure till 2004, after which the ice entrance steadily retreated till 2012, when a big a part of the floating sections have been disconnected. Because the mannequin incorporates extra correct observations of the altering fee of ice motion, it’s possible that the IPCC estimates of worldwide sea stage rise of 22-98 cm will should be adjusted upwards.

“We’re predicting profound modifications in world sea ranges which can be higher than predicted by current fashions,” mentioned co-author Eric Rigneault, a professor of Earth system science on the College of California, Irvine.

“Knowledge collected within the huge inside of an ice sheet, such because the one described right here, helps us higher signify the bodily processes concerned in numerical fashions and in flip gives extra sensible predictions of worldwide sea-level rise.”

Reference: Shfakat A. Han, Youngmin Choi, Mathieu Marlighem, Eric Rignot, Veit Helm, Angelique Humbert, Jeremy Mougineau, Romain Milan, Kurt H. Kjer, and Anders A. “Widespread inner thinning and acceleration of the Northeast Greenland Ice Stream Bjork, 9 Nov 2022 Nature.
DOI: 10.1038/s41586-022-05301-z




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