Greenland’s Petermann Glacier forms new giant iceberg | Polarjournal

Cracks in the floating ice tongue of the Petermann Glacier in the far north-west of Greenland indicate a further demolition of a large iceberg. As glaciologists from the Alfred-Wegener-Institute, Helmholtz Center for Polar and Marine Research (AWI) report in a new study, the flow rate of the glacier has increased by an average of 10 percent since an iceberg break in 2012, so that new cracks have arisen in the following period – a completely natural process. However, model simulations by the researchers show that if these ice masses also break off, the Petermann Glacier is likely to accelerate further and transport more ice into the sea, with corresponding consequences for global sea levels.

Petermann Glacier in the north-west of Greenland has produced large icebergs in the past. Its 18 km wide glacier tongue is one of the few that still swims and does not already lie on it. (Image: Andreas Muenchow)

Petermann Glacier in the far north-west of Greenland is one of the most famous glaciers in the region. On the one hand, its catchment area includes four percent of the Greenland ice sheet. On the other hand, it has a floating ice tongue like only two other glaciers of Greenland. This is currently moving over a distance of about 70 kilometers into the Petermann Fjord. Cracks about 12 kilometers above the previous glacial edge suggest that a large iceberg from the Petermann Glacier could break off again in the near future. Glaciologists from the Alfred-Wegener-Institute, Helmholtz Center for Polar and Marine Research (AWI) in Bremerhaven, come to this conclusion after analyzing satellite images of the glacier over the past ten years. “The satellite data show that the Petermann Glacier flowed at an average speed of 1135 meters per year in the winter of 2016. This was an acceleration of about 10 percent compared to the winter of 2011 and we wondered what triggered this speed increase,” says AWI glaciologist and co-author Niklas Neckel.

The satellite images show the iceberg in 2012 on the left, on the right the new cracks in the glacier tongue pushed forward. (Image: NASA / Sentinel-2)

The scientists then simulated the observed ice transport of the Petermann Glacier in a computer ice model and were able to prove that the demolition of a large iceberg in August 2012 had set in motion the acceleration of the glacier. “The ice masses of the glacier rub right and left on rock faces on their way into the sea, which frame the fjord. If a large iceberg breaks off at the end of the glacier tongue, the length of the ice tongue shrinks overall and thus also the distance on which the ice masses touch the rocks. Their braking effect decreases and the glacier begins to flow faster,” explains AWI ice modeler and first author Martin Rückamp. The computer model predicts a similar acceleration in the event of another iceberg calving. “We cannot predict when the Petermann Glacier will calve again and whether a demolition will actually reach the cracks in the glacier tongue that we have discovered,” says Martin Rückamp. “However, it is to be assumed that the glacier tongue will shrink significantly again in the event of a further demolition and that the braking effect of the rocks will decrease even further.”

In the rear, the glacier hangs on the steep rock faces, which have a braking effect on the flow speed. The less braking effect, the higher the flow speed and the more icebergs break off. (Photo: Andreas Muenchow)

The extent to which the accelerated ice transport of the Petermann Glacier is connected to various consequences of global warming has not yet been thoroughly investigated by the scientists. “We now know that the flow rate of the glacier is increasing as a result of iceberg breaks. We also observe that the frequency of such demolitions at the Petermann Glacier is increasing. However, we have not been able to investigate whether the warming atmosphere over Greenland or warmer seawater is responsible for this,” says Niklas Neckel. For the scientists, however, the acceleration of the Petermann Glacier is a signal. In contrast to the glaciers in the southeast and southwest of Greenland, the glaciers in the far north of the island have so far shown little change. That now seems to be changing. And this may well have an impact on sea levels. Because the current ice mass loss of Greenland, among other things due to the calving of icebergs, currently contributes about one-fifth to global sea level rise.

Source: Alfred Wegener Institute for Polar and Marine Research

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