A meltwater lake on Greenland's 79°N Glacier, formed in 1995, has undergone sudden drainages that are fracturing the ice in unusual triangular patterns. These events, accelerating in recent years, raise concerns about the glacier's long-term stability amid warming temperatures. Scientists are studying whether it can recover from these disturbances.
The 79°N Glacier in Greenland has experienced dramatic changes since a meltwater lake appeared on its surface in 1995, a time when rising atmospheric temperatures first allowed such features in the area. Prior to the mid-1990s, no lakes existed there, according to Prof. Angelika Humbert of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI). From 1995 to 2023, the lake drained abruptly seven times through cracks and channels, releasing massive amounts of freshwater to the glacier's edge and ocean. Notably, four of these drainages occurred in the last five years, indicating an acceleration.
These events have led to the formation of extensive triangular fracture fields on the glacier surface starting in 2019, differing from typical drainage patterns. "During these drainages, extensive triangular fracture fields with cracks in the ice formed from 2019 onwards, which are shaped differently from all lake drainages I have seen so far," Humbert explained. Some fractures evolved into large vertical shafts called moulins, spanning several dozen meters wide. Water continues to flow through these even after main drainages, reaching the ice base in mere hours and creating connected systems of channels.
The glacier's ice, behaving both viscously as it flows and elastically like a rubber band, allows cracks to form under stress and partially close over time. However, radar images reveal that surface fractures persist unchanged for years, with some visible more than 15 years after formation. In certain spots, ice heights shifted unevenly across fractures, and beneath the lake, water pooled into a subglacial reservoir, lifting the surface like a blister.
Researchers used satellite data, airborne surveys, and viscoelastic modeling to track these dynamics. "For the first time, we have now measured the channels that form in the ice during drainage and how they change over the years," Humbert noted. The findings, published in The Cryosphere in 2025, highlight the need to incorporate fracture evolution into ice sheet models, especially as warming pushes cracks farther uphill. A key uncertainty remains: whether repeated disturbances have locked the glacier into a new state or if it can still revert to seasonal norms. "These are extreme disturbances within the system, and it has not yet been investigated whether the glacial system can absorb this amount of water," Humbert said.