Meltwater lake splits Greenland ice sheet

Since the 1990s, a meltwater lake has been floating on the 79°N Glacier – one of the three main outlet glaciers of the Greenland ice sheet. This is now 21 km² in size. An international research team involving Prof. Holger Steeb from the SimTech Cluster of Excellence at the University of Stuttgart, together with partners from the Alfred Wegener Institute (AWI) and TU Darmstadt, has investigated how this lake was formed – and how repeated, abrupt drainage over many years cuts deep, triangular cracks, known as moulins, into the ice. The findings have now been published in The Cryosphere scientific journal.

In addition to the evaluation of satellite images and radar data, modelling played a key role. Viscoelastic modeling allows the complex material properties of glacier ice - its simultaneously viscous and elastic nature - to be accurately reproduced.

“The numerical models show how the drainage channels deform during and after a drainage event,” explains Holger Steeb, spokesperson for Collaborative Research Center 1313 “Interface-Driven Multi-Field Processes in Porous Media”. "The simulations explain how the cross-section of a channel changes under the influence of water and ice movement, whether it closes again over weeks and months or remains open for years and is reactivated. The behavior of these channels is crucial to understanding how quickly and to what extent meltwater from the ice sheet enters the sea."

The models thus form a bridge between observations from space and direct measurements in the field. They show why some moulins remain stable for years, while others disappear quickly. They also explain how stresses and strains in the ice affect the formation of cracks. And how the cracks accelerate the transport of meltwater to the base of the glacier.

In addition to the evaluation of satellite images and radar data, modelling played a key role. allows the complex material properties of glacier ice - its simultaneously viscous and elastic nature - to be accurately reproduced.

“The numerical models show how the drainage channels deform during and after a drainage event,” explains Holger Steeb, spokesperson for Collaborative Research Center 1313 “Interface-Driven Multi-Field Processes in Porous Media”. "The simulations explain how the cross-section of a channel changes under the influence of water and ice movement, whether it closes again over weeks and months or remains open for years and is reactivated. The behavior of these channels is crucial to understanding how quickly and to what extent meltwater from the ice sheet enters the sea."

The models thus form a bridge between observations from space and direct measurements in the field. They show why some moulins remain stable for years, while others disappear quickly. They also explain how stresses and strains in the ice affect the formation of cracks. And how the cracks accelerate the transport of meltwater to the base of the glacier.

Since the supraglacial lake was first observed in 1995, there have been a total of seven drainage events – four of them in the last five years alone. Since 2019 in particular, new types of large, triangular fracture fields have been emerging. These moulins have openings measuring several dozen meters and channel huge amounts of water to the base of the ice sheet within hours.

“The viscoelastic material behavior of glacier ice is central to these processes,” says Holger Steeb. "The elastic component allows cracks to form, while the viscous component ensures that channels close again over time – or reopen in subsequent years under certain conditions. We were able to reproduce precisely this interaction using numerical simulations."

The new findings are not only significant for glaciology, but also for climate research, coastal protection, and political decision-making. By integrating the processes of crack formation and drainage into ice sheet models, future meltwater volumes and their impact on global sea level rise can be estimated more accurately. This is an important basis for assessing risks to coastal regions worldwide, planning protective measures, and better limiting the consequences of climate change.

The study was conducted in collaboration between the SimTech Cluster of Excellence and the Institute of Mechanics (Civil Engineering) at the University of Stuttgart, the Alfred Wegener Institute, TU Darmstadt, and other international partners.

Original publication:
Humbert, A., Steeb, H., et al. (2025): Insights into supraglacial lake drainage dynamics: triangular fracture formation, reactivation and long-lasting englacial features. The Cryosphere. https://doi.org/10.5194/tc-19-3009-2025