A Greenland glacier is cracking open in real time
A meltwater lake that formed in the mid-1990s on Greenland’s 79°N Glacier has been draining in sudden, dramatic bursts through cracks and vertical ice shafts. These events have accelerated in recent years, creating strange triangular fracture patterns and flooding the glacier’s base with water in just hours. Some drainages even pushed the ice upward from below, like a blister forming under the glacier. Scientists now wonder whether the glacier can ever return to its previous seasonal rhythm.
Scientists first detected the lake in observational records from 1995. Before then, no lakes had existed in this part of the 79°N Glacier. "There were no lakes in this area of the 79°N Glacier before the rise in atmospheric temperatures in the mid-1990s," said Prof. Angelika Humbert, a glaciologist at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI).
After forming in 1995, the lake did not remain stable. "From the time of its formation in 1995 until 2023, the lake's water repeatedly and abruptly drained through channels and cracks in the ice, causing massive amounts of fresh water to reach the edge of the glacier tongue towards the ocean." Researchers identified seven major drainage events in total, with four occurring within just the last five years.
Unusual Ice Fractures and Giant Vertical Channels
As these sudden drainages took place, the glacier surface began to fracture in unexpected ways. "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 said. Some of the fractures developed into large vertical shafts known as moulins, with openings that can span several dozen meters.
Even after the main lake drainage ends, water continues flowing through these moulins. This allows enormous volumes of meltwater to reach the base of the ice sheet within just a few hours. "For the first time, we have now measured the channels that form in the ice during drainage and how they change over the years."
Why the Glacier Cracks and Then Heals
Following the lake's formation in 1995, its surface area gradually shrank as cracks began to appear. In recent years, however, drainage events have happened more frequently. "We suspect that this is due to the triangular moulins that have been reactivated repeatedly over the years since 2019," Humbert explained.
This behavior is linked to how glacier ice responds to stress. Ice flows slowly like an extremely thick (viscous) fluid as it moves over the ground beneath it. At the same time, it behaves elastically, meaning it can bend and partially return to its original shape, similar to a rubber band. This elasticity makes it possible for cracks and channels to form. Meanwhile, the slow flowing nature of the ice helps those channels gradually close again after a drainage event.
"The size of the triangular moulin fractures on the surface remains unchanged for several years. Radar images show that although they change over time inside the glacier, they are still detectable years after their formation." The data also shows that the glacier contains a connected system of cracks and channels, providing multiple routes for water to escape.
Meltwater is lifting the glaciers
Aerial images revealed shadows tracing many of the surface cracks. In some cases, the ice on either side of a fracture appeared uneven. "In some cases, the ice at the fracture surfaces has also shifted in height, as if it were raised more on one side of the moulin than on the other," Humbert noted.