Large ice stream in Greenland melts more and faster | Polarjournal
The two largest parts of the Northeast Greenland Ice Stream, the Zachariae Ice Stream and the Nioghalvfjerdsbrae have already been under observation for 10 years. In 2012, the glacier tongue that had previously slowed the flow of ice into the sea disintegrated. Since then, the ice masses have been pouring into the Fram Strait at a faster rate than previously thought. Image: Angelika Humbert, AWI

Attention is currently focused on the World Climate Summit in the Egyptian resort of Sharm-el-Sheik. Decisions are to be made there to curb the effects of the ever warmer climate. This includes the rise in sea level, which is rising little but inexorably. One of the largest ice streams in Greenland will contribute significantly to this, as an international study shows. Because it is melting faster than previously thought.

More extensive thinning in the inland part of the Northeast Greenland Ice Stream discharges much faster and more ice into the adjacent Greenland Sea at the front, which in turn will cause six times greater sea level rise by 2100. This is the result of the study by Sfaqat Khan, professor at the Danish Technological University in Copenhagen, and an international team of experts from the USA, France, Denmark and Germany. The researchers relied on a new approach of satellite and aircraft-based remote sensing methods and high-sensitivity GPS transmitters deployed much farther on the ice sheet than previously. This enabled them to measure both height differences and flow velocities of the ice sheet and to make calculations on mass loss. The work was published this week in the prestigious journal Nature.

The area of the Northeast Greenland Ice Stream has been under closer observation for a long time. For it was here, in 2012, that the floating glacier tongue that had been slowing down the system of glaciers of the Greenland Ice Sheet behind it had broken apart. After all, about 12 percent of the entire Greenland ice sheet converges in this region and now also flows into the sea. With up to 100 kilometers per year, the ice masses flow into the sea, according to the latest data from Khan and his colleagues after analyzing satellite-based GPS data. The novelty of the study was that it was possible to collect data much further inland than before. These showed that there, as well as in front, the ice sheet thins out (decreases in height) and there the ice also flowed much faster than previously thought. “Our data show us that what we see happening at the front reaches far back into the heart of the ice sheet,” Khan explains. “We can see that the entire basin is thinning, and the surface speed is accelerating.” Khan explains.

Greenland is known for its numerous icebergs. The largest and most tabular came from the northeastern region. Their melting promotes sea level rise. Image: Dr Michael Wenger

Using the data the team had obtained from the GPS transmitters and satellite imagery, they predicted a correction for the proportion of sea level rise. They predict between 13.5 and 15.5 millimeters by the year 2100, about five to six times more than previous studies have predicted. These only came to 1.5 to 3.5 millimeters. And the warmer it gets, the faster the glaciers flow, thinning further at the back and retreating further at the front, releasing more and more ice in the form of icebergs, whose melting causes the sea to rise further. “Under present day climate forcing, it is difficult to conceive how this retreat could stop,” says Sfaqat Khan. For participants at the World Climate Summit, where they will also debate how to mitigate the effects of sea level rise on developing countries and their inhabitants, the study’s findings are unlikely to be good news. And for the residents of Sharm-el-Sheik, even less so.

Dr Michael Wenger, PolarJournal

Contributed image: Zachariae Eisstrom, Nicolaj Krog Larsen

Link to study: Khan, S.A. (2022) Nature: Extensive inland thinning and speed-up of Northeast Greenland Ice Stream;

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