Next year, scientists will deploy a swarm of aerial drones, autonomous submarines and ice sensors in a major coordinated effort to better understand how and why icebergs break off from the Greenland ice sheet.
The , which is backed by £16 million of funding from the UK’s Advanced Research and Invention Agency (ARIA), aims to improve estimates of how much fresh water is entering the North Atlantic from Greenland ice melt.
The answer is crucial for delivering accurate predictions of the rate of sea level rise the world can expect over the coming century. It will also help scientists determine how quickly the Atlantic meridional overturning circulation (AMOC), a vital ocean current that transports nutrients and warm water from the tropics to northern Europe, will weaken in response to climate change.
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Scientists are worried a huge influx of cold meltwater from the Arctic could weaken the AMOC to the point of irreversible collapse, perhaps within decades, an outcome that would have devastating effects on the UK and northern Europe. But there remains huge uncertainty over the timing of any potential collapse.
“The whole idea of GRAIL is really to get how quickly the Greenland ice sheet is melting and how quickly that meltwater, that fresh water, gets into the North Atlantic,” says at the British Antarctic Survey, the organisation leading the GRAIL project.
Iceberg calving is particularly important to understand because calving events can destabilise inland ice, which will then make its way to the ocean, says at the University of Cambridge, who isn’t involved in the project. “If you calve away at the edge of a floating ice tongue, then it will remove a buttressing on the inland ice,” he says. “It will allow the inland ice to flow more rapidly.”
But accurately assessing the calving of icebergs from Greenland glaciers is notoriously difficult and dangerous. It requires researchers to get instruments up close to towering ice cliffs – which could break away at any moment – to measure the temperature, salinity and turbulence of the water butting against the ice. “This is a very precarious and dangerous place to work,” says Hogan.
Instead of deploying human researchers for this task, the GRAIL project will use a fleet of autonomous submarines and aerial drones, ranging in size from 4 metres to 1 metre in length, to take measurements when the first expedition begins in 2026. The vehicles are being fine-tuned with additional sensors and software to enable them to operate as a network in the harsh Arctic environment. They will all be deployed simultaneously in a series of coordinated missions at two specific glaciers, using the UK’s polar research vessel, RSS Sir David Attenborough, as an expedition mothership, says Hogan. “It’s a new way of working,” she says.
The scale of the project is “remarkable” says at the University of Sheffield, UK, who isn’t involved in GRAIL. “There’s certainly a lot of scientific power in being able to apply everything at once,” he says. But he warns the research effort will be technically challenging, particularly given the extent of the equipment involved. “It’s logistically very complex to get all of that to work at the same time, in the same place, in an incredibly remote location,” he says.
If successful, the data collected on the expedition will be analysed and fed into the state-of-the-art climate models scientists rely on to predict sea level rise and the risk of the AMOC shutdown. The team expects the data to have a “real impact” on climate model outputs, says Hogan.
The GRAIL findings will also contribute to a wider ARIA initiative to , which could provide advance alerts of major, irreversible changes in Earth systems.
