Cracks herald the calving of a large iceberg from Petermann Glacier

[Judi Lynn]

February 06, 2019

Cracks in the floating ice tongue of Petermann Glacier in the far northwest reaches of Greenland indicate the pending loss of another large iceberg. As glaciologists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) report in a new study, the glacier's flow rate has increased by an average of 10 percent since the calving event in 2012, during which time new cracks have also formed - a quite natural process. However, the experts' model simulations also show that, if these ice masses truly break off, Petermann Glacier's flow rate will likely accelerate further and transport more ice out to sea, with corresponding effects on the global sea level. The study was recently released in the Journal of Geophysical Research: Earth Surface and is freely available.

Located in the outermost northwest corner of Greenland, Petermann Glacier is one of the most prominent glaciers in the region: partly because its catchment encompasses four percent of the Greenland Ice Sheet, and partly because it is one of only three glaciers in Greenland with a floating ice tongue. That tongue currently extends roughly 70 kilometres into Petermann Fjord. Cracks 12 kilometres above the previous glacier edge indicate that, in the near future, another major iceberg could calve from Petermann Glacier.

Glaciologists at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) in Bremerhaven came to this conclusion after analysing satellite imagery of the glacier from the past ten years. "The satellite data shows that Petermann Glacier had a flow speed of roughly 1135 metres per year in the winter of 2016. That equates to an acceleration of about 10 percent in comparison to the winter of 2011, and we asked ourselves what was responsible for the increased speed," explains AWI glaciologist and co-author Niklas Neckel.

Fjord sidewalls serve as stabilizing effect to the glacier

The researchers subsequently simulated the glacier's observed ice transport in a computer model and were able to confirm that the loss of a large iceberg in August 2012 is what triggered the acceleration. "On their way to the sea, the glacier's ice masses rub along the rock walls that enclose the fjord to the left and right. If a major iceberg breaks away from the end of the glacier's tongue, it will reduce the tongue's overall length, and with it, the route along which the ice masses scrape against the stone. This in turn limits the walls' braking effect, so that the glacier begins flowing faster," explains AWI ice modeller and first author Martin Rückamp.

More:
https://www.brightsurf.com/news/article/020619475584/cracks-herald-the-calving-of-a-large-iceberg-from-petermann-glacier.html





Earlier story:

NASA IMAGES REVEAL HUGE NEW CRACK ON GREENLAND’S PETERMANN GLACIER
BY HANNAH OSBORNE ON 4/18/17 AT 8:28 AM

A huge new crack has appeared on the Petermann Glacier, a large ice shelf in northern Greenland. NASA images show the rift has opened up at the center of the floating ice shelf and, should it continue to grow, it could break off into a large iceberg and float away.

NASA took the aerial images of the glacier on April 14 as part of its Operation IceBridge mission. This aims to better understand how the polar regions are connected to the global climate system. Researchers chart changes in the thickness of sea ice, ice sheets and glaciers, as well as looking at how the Earth’s poles respond to climate change.

Normally, cracks in ice shelves appear near the edges, where the ice is thinner. The location of the new crack at the center of the Petermann Glacier makes it of particular concern. It means another process must be causing the ice shelf to thin. Scientists believe there could be warm water sitting beneath the ice shelf, but say they will need to undertake further research to confirm this.

More:
https://www.newsweek.com/nasa-ice-shelf-crack-iceberg-images-petermann-glacier-585396

More images of the Petermann Glacier:

https://tinyurl.com/ycw3r46d

[Bayard]

1. Ah boy....

Never any good climate news.