An enormous meltwater flood beneath the Greenland ice sheet generated enough pressure to crack the glacier, forcing water to erupt at the surface—defying existing climate models and prompting scientists to reassess the complexity of global warming.
This marks the first time such a phenomenon has been observed, raising new concerns about the increasingly hazardous effects of meltwater driven by climate change. Crucially, current models attempting to predict the Greenland ice sheet’s future behavior do not account for meltwater pressure, revealing a significant blind spot in our understanding of Earth’s evolving climate.
Observing the Unexpected
The study, led by the Lancaster University Centre of Excellence in Environmental Data Science and the UK Centre for Polar Observation and Modelling, focused on a previously known subglacial lake beneath the Greenland ice sheet. Researchers utilized satellite data from ESA and NASA missions, combined with three-dimensional surface models from the ArcticDEM project.
Analysis revealed that in the summer of 2014, 90 million cubic meters of water surged out of an 85-meter-deep crater in the ice sheet over just 10 days. One of the largest subglacial floods ever recorded, the volume of water released during that period matched the amount that flows over Niagara Falls in roughly nine hours at peak season.
Further down the ice sheet, researchers identified 385,000 square meters of fractured and warped ice in an area previously characterized by smooth terrain. They also discovered a freshly scoured ice surface twice the size of New York City’s Central Park.
“When we first saw this, because it was so unexpected, we thought there was an issue with our data,” said lead author Dr. Jade Bowling. “However, as we went deeper into our analysis, it became clear that what we were observing was the aftermath of a huge flood of water escaping from underneath the ice.”
Describing a More Complex Global Warming
“The existence of subglacial lakes beneath the Greenland Ice Sheet is still a relatively recent discovery, and—as our study shows—there is still much we don’t know about how they evolve and how they can impact on the ice sheet system,” said Dr. Bowling.
“Importantly, our work demonstrates the need to better understand how often they drain, and, critically, what the consequences are for the surrounding ice sheet.”
This event is the first documented instance of meltwater flowing upward. Until now, scientists believed meltwater traveled only downward—starting at the surface, reaching the base of the glacier, and ultimately draining into the ocean. Another surprise was that models had predicted the region to be filled with ice frozen to the bedrock, suggesting that intense subglacial pressure may have fractured the ice in unexpected ways.
Because current climate models do not account for such processes, it’s clear that meltwater behavior is even more complex than previously thought—underscoring the need for updates as melting accelerates due to global warming.
Continuing to Monitor a Changing Climate
“This research demonstrates the unique value of long-term satellite measurements of Earth’s polar ice sheets, which – due to their vast size – would otherwise be impossible to monitor,” said co-author Professor Malcom McMillan. “Satellites represent an essential tool for monitoring the impacts of climate change and provide critical information to build realistic models of how our planet may change in the future. “This is something that all of us depend upon for building societal resilience and mitigating the impacts of climate change.”
“What we have found in this study surprised us in many ways,” added co-author Dr Amber Leeson. “It has taught us new and unexpected things about the way that ice sheets can respond to extreme inputs of surface meltwater, and emphasised the need to better understand the ice sheet’s complex hydrological system, both now and in the future.”
“Given the control that subglacial hydrology has on the dynamics of the ice sheet, it is critical that we continue to improve our understanding of these hidden, and poorly understood, hydrological processes, and these satellite observations are key to that,” Leeson concluded.
The paper “Outburst of a Subglacial Flood from the Surface of the Greenland Ice Sheet” appeared on July 30, 2025, in Nature Geoscience.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.