July 12, 2024

Greenland: Reducing ice loss – wissenschaft.de

Greenland: Reducing ice loss – wissenschaft.de

Again, upward correction: In northeastern Greenland, ice loss could be six times what was previously assumed by the end of the century, and thus contribute significantly to sea level rise. This comes from a combination of global positioning system (GPS) and satellite data documenting the widespread strengthening and easing of ice flow in the northeastern part of the island’s ice sheet. Scientists fear that ice dynamics may be underestimated in other areas of Greenland.

With so many concerns about climate change, a particularly concerned look is being directed at the largest island on Earth: the Greenland Ice Sheet, sometimes more than three kilometers thick, threatens to turn more and more into water and thus raise global sea levels. It is not only the melting of glacier surfaces due to rising temperatures that plays a role: the ice giants are also increasingly sliding and thus flowing faster into the sea. To date, however, the extent and further development of this effect remains unclear. In particular, information from the remote northeastern region of Greenland is still missing so far. An enormous stream of ice flows there: it connects the interior of the ice sheet with two glaciers at a distance of 600 km, which causes about 12 percent of the Greenland ice sheet to drain into the sea.

Targeting a glacier in northeastern Greenland

In 2012, after decades of melting, the floating ice caps collapsed and the ice has retreated at an accelerating rate since then. The loss is related to the diminishing of the braking effect on the ice flow. However, it is not yet clear how much ice is lost as a result, and how far the impact extends to the ice sheet. Because this region of the ice sheet moves only less than one meter per year and is therefore relatively difficult to monitor, accurate predictions have only been possible to a limited extent. “The models are mainly based on observations at the front of the ice sheet, which is easily accessible and where there is a lot of activity,” says lead author Shafqat Abbas Khan of the Technical University of Denmark in Lyngby.

To provide further clarity, Khan and colleagues from 2016 to 2019 collected data from GPS stations up to 200 kilometers within the Northeast Greenland Glacier Stream. They then combined this information with altitude data from the CryoSat-2 satellite mission. The results then formed the basis for model simulations that shed light on the processes in the ice sheet and present further developments. “We were able to detect subtle changes in velocity, which, when combined with the ice flow model, ultimately give us insight into how the glacier slides over its bottom,” says co-author Matthew Morlighem of Dartmouth College in Hanover.

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As the researchers report, their results show that the extent of ice loss has thus far been underestimated. “Our data shows that what we see in the foreground extends well into the ice sheet,” Khan said. “We can see that the entire basin is weakening and the surface velocity is accelerating. Every year, the glaciers we study are retreating inland, and we expect this to continue for decades and centuries to come. Under current climatic conditions, it is hard to imagine how this retreat can be stopped,” he says. says the world.

Model calculations based on the data indicated that glacial flow in northeastern Greenland could contribute six times to sea level rise by 2100 as previously estimated. Specifically, this is an increase of between 13.5 and 15.5 mm. Scientists say this is equivalent to the contribution of the entire Greenland ice sheet over the past 50 years.

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“It’s possible that what we’re seeing in northeastern Greenland is happening in other areas of the ice sheet as well. This is because many glaciers have accelerated and diminished near the edge in recent decades,” says Morlegim. “Using GPS data, we can now also determine the inward extent to which this acceleration is spreading. If this is robust, the contribution of ice dynamics to the overall mass loss of Greenland would be greater than what current models suggest,” concludes co-author Eric Regno of The University of California, Irvine notes that: “Data collected in the vast interior of ice sheets, such as the one shown here, can help us better represent physical processes in numerical models in the future, which in turn will lead to more realistic predictions of surface level rise. sea ​​in the world.

Source: Technical University of Denmark, professional article: Nature, doi: 10.1038/s41586-022-05301-z