A hidden lake beneath the Greenland Ice Sheet unexpectedly drained more than a decade ago, fracturing the ice surface and forming a large crater — an event only recently uncovered by Earth-observing satellites.
The massive ice sheet, located in a remote region of northern Greenland, harbors a subglacial lake that appears to have flooded in 2014, releasing 23.8 billion gallons (90 million cubic meters) of meltwater over the course of 10 days — roughly equivalent to nine hours of peak flow over Niagara Falls.
The meltwater from the subglacial lake surged upwards, the satellites showed, bursting through the ice surface. The rapid flooding that followed carved a crater 279 feet (85 meters) deep and 0.77 square miles (2 square kilometers) wide into the surface of the ice sheet. The flood’s upward force also lifted blocks of ice 82 feet (25 meters) above the surface and left behind deep fractures and scoured markings, according to a statement from the European Space Agency (ESA).
“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,” Jade Bowling, lead author of the study from Lancaster University, said in the statement. “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 startling event was discovered using data from multiple Earth-observing satellites, including ESA’s CryoSat, the Copernicus Sentinel-1 and Sentinel-2 missions, and NASA’s ICESat-2, as well as 3D models of the ice sheet surface from the ArcticDEM project. The amount of meltwater released from underneath the ice in 2014 is considered one of the largest recorded subglacial floods in Greenland, according to the statement.
Beyond revealing the dramatic surface changes, the satellite data has reshaped scientists’ understanding of how water behaves under ice. Previously, scientists believed meltwater generally flowed down from the surface to the ice base, eventually draining into the ocean. This study shows that water can also flow upward, forced through the ice by intense pressure, even in areas previously thought to have frozen beds.
This upward surge of water fractured the overlying ice sheet, creating new channels for the water to escape. This kind of upward water flow could affect how ice sheets respond to a warming world, which has not yet been accounted for in current climate models. Understanding these processes is key to improving predictions of Greenland’s contribution to future sea-level rise, the researchers said.
Their findings were published on Wednesday (July 30) in the journal Nature Geoscience.
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