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"I saw a little line and thought it was new," says Lhermitte as he describes the discovery he made, almost by accident, when testing a thaw detection methodology that requires making animated GIFs with the grainy black and blue images of Greenland captured by the Sentinel-1 satellite of the European Space Agency.
Lhermitte, an assistant professor at the Technical University of Delft in the Netherlands, reviewed the records of another satellite and saw the crack that appeared in July 2016 but, to his knowledge, had not been seen by anyone.
Greenland is responsible for nearly a third of the sea level rise Earth is experiencing, so a new rift and potential breakout of one of its largest glaciers is a cause for concern.
Lhermitte took his discoveries directly to Twitter, with messages in which he shared several images of the rift and sought help determining its importance. “Many of my first tweets were between question marks. I had a hypothesis, but I wasn't sure, ”he says.
His tweets caught the attention of Tom Wagner, NASA's cryosphere program scientist and director of polar research. Wagner, in turn, connected him with a member of his team, Joe MacGregor.
Just at that time, MacGregor was in Greenland leading a unique research campaign, making low-altitude flights over the Greenland and Antarctic ice sheets to create 3-D images to understand the rapid changes they are experiencing.
MacGregor says Wagner wrote him an email "asking if we had flown over the area of the rift he had pointed out."
And, how is the destination, the campaign still had one flight over the Petermann Glacier for this year's mission and it was just scheduled for the next day. The crack that Lhermitte found was only a few hundred meters from the path of that flight, a flight that according to MacGregor "was already the most important over Petermann Glacier."
"Everything came together perfectly," says MacGregor. "Even the weather cooperated," as a sunny sky allowed a very clear image to be taken of the ice surface below.
NASA's research campaign flight confirmed the existence of the crack and scientists were able to make a detailed map of the area, thanks to sophisticated equipment on board the plane.
This new crevasse is important because it is much higher than the last crevasses discovered in that glacier. The higher up it is, along with an eventual glacier breakout on an ice island, the more unstable that ice sheet will be.
The glacier acts as a barrier between the ice sheets and the open ocean and as the glacier recedes and large chunks of ice break up and end up in the ocean, it will have less resistance. All of this accelerates the rise in sea level.
The new rift also indicates that an iceberg could potentially break the glacier. That has happened twice this decade: in 2010 and 2012. According to MacGregor, the breakup that has occurred above and comes shortly after two major breakups, "is extremely unusual, if not unprecedented." .
Glacial retreat doesn't just affect Petermann. It has become common in many of the largest and most important glaciers in Greenland, which is why it is very important to do research in these regions.