Fissures caused by melting of the Greenland ice sheet are threatening its stability, and now drone footage has shown the resulting water drainage is occurring more quickly than previously thought.

Melting of this ice sheet – the second largest in the world, with three million cubic kilometres of ice that is two kilometres thick on average – has the largest impact on rising sea levels globally.

“If it were to melt entirely, sea levels would rise by over seven metres,” says lead author Tom Chudley from the Scott Polar Research Institute at the University of Cambridge, UK, “although we don’t expect that to happen in the foreseeable future.”

Nonetheless, he adds, it is currently contributing to sea level rise of one millimetre per year – higher than predictions just a few years ago – and the rate is increasing faster than losses from other ice masses around the globe.

As the weather warms each summer, satellite images show increasing numbers of lakes have been forming on the sheet’s surface which flow within hours through more than a kilometre of ice to its base.

“Our previous work has shown that faster ice flow leads to more fractures,” says team leader Poul Christoffersen. This chain reaction can cause drainage of other lakes up to 80 kilometres away and accelerate the rate of sea level rise.

To get a closer look at how the fractures form, the researchers flew custom-made drones suited to extreme Arctic conditions on autopilot over a kilometre-wide lake that had formed on the surface of the ice sheet at Store Glacier in northwest Greenland.

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