A sudden and dramatic event unfolded beneath the Greenland ice sheet at Harder Glacier when a hidden subglacial lake burst, sending an explosive surge of water upward through thick ice. Over just ten days, 23.8 billion gallons (90 million cubic meters) of water—equivalent to nine hours of Niagara Falls at full flow—were released. The force created an 85-meter (270-foot) deep crater covering 2 square kilometers (0.77 square miles). This unprecedented flood not only reshaped the surface but challenged scientific understanding of how meltwater behaves under ice sheets.
The Greenland ice sheet is Earth’s second-largest body of ice, covering about 80% of Greenland and holding enough frozen water to raise global sea levels by approximately 7 meters (23 feet). Recent decades have seen it melt and shift at accelerating rates, driven by warm ocean currents eroding its base and rising air temperatures intensifying surface melt. Meltwater from Greenland now significantly contributes to sea level rise, with flow rates doubling in recent decades. The influx of freshwater into the North Atlantic also threatens to disrupt the Atlantic Meridional Overturning Circulation (AMOC), a critical climate-regulating system.
Downstream from the burst, researchers discovered an ice-scoured landscape resembling a war zone. Towering 25-meter (82-foot) ice blocks had been ripped from the ground, deep cracks fractured the surface, and the floodwaters had carved through an area twice the size of Central Park. Dr. Jade Bowling of Lancaster University, lead author of the study published in Nature Geoscience, initially doubted the satellite data due to its sheer scale. Further analysis confirmed it as the aftermath of a massive subglacial flood.
What made the event particularly remarkable was its reversal of expectations. Typically, meltwater drains downward from the surface to the base of an ice sheet. Here, the water surged upward, shattering solid ice layers in the process—something not accounted for in current climate or ice-flow models. Even more puzzling, the location’s ice bed was thought to be permanently frozen, yet pressure evidently fractured it, allowing the lake to drain violently.
The team relied on high-resolution ArcticDEM topographic maps and data from ESA’s CryoSat, Sentinel-1 and -2, and NASA’s ICESat-2 satellites. Without these tools, the event would have gone unnoticed, underscoring the vital role of long-term satellite monitoring in tracking polar ice dynamics and informing climate models.
This event exposes critical gaps in our understanding of subglacial hydrology and its influence on ice sheet stability. With surface melt increasing under global warming, more water may accumulate beneath the Greenland ice sheet, raising the likelihood of further high-pressure releases that could destabilize ice structures. Such events could accelerate ice loss, sea level rise, and changes to ocean circulation.
The research was a multinational effort involving scientists from the U.K., Europe, and the U.S., with funding from the U.K. Natural Environment Research Council, ESA, and UKRI. Experts stress that understanding Arctic hydrology is essential for predicting how the Greenland ice sheet will evolve in a warming climate—and for preparing for the profound global impacts of its changes.