The massive Petermann Glacier looks like it is ready to calve

Something caught Stef Lhermitte’s eye last week as he pored over satellite images of Northwest Greenland’s Petermann Glacier, one of the largest glaciers in Greenland.

“I saw a small line and thought ‘that seems new,’ ” said Lhermitte as he described the discovery he made, almost by accident, as he was testing a methodology to detect melt that requires making animated GIFs from the black and blue grainy images of Greenland captured by the European Space Agency’s Sentinel-1 satellite.

Lhermitte, an assistant professor at Delft University of Technology in the Netherlands, checked other satellite records and determined the crack showed up in July 2016, but to his knowledge, had not been noticed by anyone.

Greenland is responsible for about one-third of the sea-level rise the Earth is experiencing, so a new crack and potential breaking off of one its largest glaciers is concerning.

Perfect timing

Lhermitte took his findings directly to Twitter, tweeting several images of the crack and searching for help determining its significance.

“Several of my initial tweets […]