Satellite Images Reveal Cracks In Major Greenland Glacier Indicating Possible Calving Event

Left: An ASTER satellite shot acquired shortly after the 2012 calving event. Right: a Sentinel-2 shot on July 31, 2018 showing the new cracks. ASTER/Sentinel-2

New satellite data has shown the state of a monolithic floating glacier in Greenland and, unsurprisingly, it ain’t looking good.

Stretching across the far northwest reaches of Greenland, the Petermann Glacier is the longest floating glacier in the Northern Hemisphere. It is one of only three glaciers in Greenland with a floating ice tongue, a 70-kilometer (43 miles) platform that extends beyond the shoreline and floats on the water.

In 2012, the glacier’s northern tip developed a colossal crack that caused a 130-square-kilometer (50 square miles) iceberg – that’s twice the area of Manhattan – to break away. Ever since this calving event, the glacier’s flow rate has increased by an average of 10 percent, as detailed in the Journal of Geophysical Research: Earth Surface,

“We now know that the loss of icebergs increases the glacier's flow rate. In addition, we've observed that calving events on Petermann Glacier are happening more frequently,” Niklas Neckel, study co-author and glaciologist at Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), said in a statement.

“But the question of whether these changes are due to the warming atmosphere over Greenland, or to warmer seawater, isn't an aspect that we could investigate using the satellite data.”

That said, a 2013 study in Nature found that climate change may cause Petermann, along with other Greenland glaciers, to thaw and contribute to sea level rise.

A number of menacing cracks have also cropped up along the tongue. Minor cracks are usually a natural process for a glacier. However, in this instance, it runs the risk of more icebergs to chip off, resulting in the glacier’s flow rate increasing even more.

“We can't predict when Petermann Glacier will calve again, or whether a calving event would actually calve along the cracks we identified in the ice tongue," explained Martin Rückamp, ice modeler at AWI. "But we can safely assume that, if it does come to a new calving event, the tongue will retreat considerably, and the rock's stabilizing effect will further decline."

The researchers used data from the Sentinel-2 Earth observation satellite, which was then used to create different simulations and models of the glacier’s future behavior. Along with detailing its increase glacier flow rate, the modeling also highlighted how more ice masses snapping off could transport more ice out to sea, which further fuels the vicious circle. 

"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,” added Rückamp “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.”

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