Violent subglacial flood fractured Greenland's ice in never-before-seen event

Yahoo

a day ago

A massive subglacial flood punched its way through the Greenland Ice Sheet in 2014, but it's only now that scientists have pieced together how and why.
New research reveals that a previously undetected lake beneath the ice drained with such explosive force that it fractured the thick ice above and burst out across the surface.
This is the first time scientists have observed such an upward-moving flood in Greenland, and it's challenging long-held assumptions about how meltwater behaves beneath ice sheets.
Ice shredded, not melted
The event unfolded over ten days in a remote region of northern Greenland. Using satellite data from NASA and the European Space Agency, along with high-resolution surface maps from the ArcticDEM project, researchers tracked the dramatic drainage of a hidden subglacial lake.
About 90 million cubic meters of water, roughly the volume of nine hours of peak Niagara Falls flow, escaped from beneath the ice, carving an 85-metre-deep crater across two square kilometers of ice surface. It stands among the largest subglacial floods ever recorded in Greenland.
But what stunned the scientists even more was what they found downstream.
In an area that had previously shown no signs of instability, they discovered a newly fractured ice landscape.
Over 385,000 square meters, about the size of 54 football fields, was covered in deep crevasses and towering, 25-meter-high upturned ice blocks.
Surrounding this zone was another six square kilometers of scoured terrain, nearly twice the size of New York's Central Park.
The scale and violence of the flood left researchers with little doubt about the power of water moving beneath the ice.
https://www.youtube.com/watch?v=Q3DlWjPMDlQ&t=2s
Lead author Dr Jade Bowling, who conducted the work during her PhD at Lancaster University, said the findings were initially hard to believe.
'When we first saw this, we thought there must be a problem with the data,' she said. 'But the more we looked, the clearer it became that we were seeing the aftermath of an enormous flood that forced its way up through the ice.'
Models missed the rupture
Until now, most models of Greenland's ice sheet assumed that meltwater moves from the surface down through the ice, eventually draining into the ocean.
This study shows that, under extreme pressure, subglacial water can move in the opposite direction, fracturing the ice from below and exploding upward.
Because most models don't include these mechanisms, they may be underestimating the ice sheet's vulnerability.
Even more surprisingly, the flood occurred in a region where the bed of the ice sheet was thought to be frozen solid.
That led researchers to propose a new mechanism: extreme water pressure caused fracturing along the ice base, which in turn allowed the water to erupt through the ice and escape at the surface.
'The Greenland Ice Sheet contains enough ice to raise global sea levels by more than seven meters,' Bowling said. 'Understanding how subglacial water moves and disrupts the ice is critical for predicting its future behavior.'
'This flood shows us that the ice sheet can respond in ways we didn't expect,' said co-author Dr Amber Leeson, a glaciologist at Lancaster University. 'It's a wake-up call to dig deeper into the processes we still don't fully understand.'
Professor Mal McMillan, co-director of the UK Centre for Polar Observation and Modelling, emphasized the importance of satellite data in detecting such hidden events. 'This kind of event would have gone unnoticed without long-term satellite data,' he said. 'It shows how critical these observations are for tracking climate change in real time.'
Because most ice sheet models assume meltwater travels only downward or laterally to the ocean, they overlook the possibility of upward-directed floods like this one. That blind spot could impact projections of how quickly the Greenland Ice Sheet is destabilizing in a warming world.
As climate change continues to intensify surface melting and expand it into new areas, such extreme water surges may become more frequent.
To keep pace, scientists say models must evolve to reflect the full complexity of subglacial hydrology. Continued monitoring from missions like ESA's CryoSat and NASA's ICESat-2 will be vital for detecting hidden lakes and tracking how they behave.
The study was a massive international effort, involving researchers from over a dozen institutions, including Lancaster University, Northumbria University, the Geological Survey of Denmark and Greenland, the University of California, the Alfred Wegener Institute, DTU Space, and the University of Leeds.
The findings have been published today in Nature Geoscience.