Massive calving episode in Greenland may foreshadow more rapid ice sheet loss
In November 2025, a study led by Adrien Wehrlé, a researcher in the Department of Geography at the University of Zürich, Switzerland, looked at the massive calving response of one of West Greenland's active glaciers, Sermeq Kujalleq in the Kangia icefjord (SKK), to the drainage of two surface lakes. Called supraglacial lakes, these are temporary meltwater ponds that form and accumulate in depressions or holes on the surface of glaciers and ice sheets.
Using satellite and terrestrial radar observations, the researchers studied SKK's response to the drainage of two supraglacial lakes in July 2022. The study is published in the journal Nature Geoscience.
SKK, also known as the Jakobshavn glacier, is a large and rapidly retreating outlet glacier on the Greenland ice sheet. As one of the world's fastest-moving and most active ice streams in West Greenland, it discharges more than 50 gigatons of ice into the ocean each year.
Rising temperatures and increased melting will cause larger lakes that may increase the frequency and magnitude of drainage events, further degrading glaciers and contributing to sea-level rise.
How lake drainage destabilized the glacier
Between July 21 and 24, two supraglacial lakes 13 kilometers (8 miles) south of SKK and 25 kilometers (16 miles) from the glacier's edge released a catastrophic surge of fast-flowing meltwater that propagated all the way to the glacier's lowest depths.
This unusual event is an example of a process chain from a lake drainage event to a resulting calving episode, demonstrating the influence that an increase in glacier flow upstream can have on Greenland tidewater glaciers at large. A drainage event sends a sudden pulse of meltwater to the bottom of the glacier, lubricating it and resulting in faster flow.
Similar to a traffic jam suddenly clearing, this rapid flow pushes material forward and destabilizes the glacier edge. The stress from this acceleration forces open pre-existing cracks at the glacier front, leading to a cascade of calving events.
A chain reaction at the terminus
In this case, the rapid drainage event in July resulted in a subglacial flood at the base of the ice stream that lubricated the bottom of outlet glaciers and rapidly accelerated ice flow. Though the regular flow speed of SKK is around 7 kilometers per year, this acceleration created a surface speed-up pulse that traveled more than 16 kilometers (10 miles) downstream within four hours.
This speed-up flow, equivalent to a walking pace of around 2.5 miles per hour, lasted for 24 hours and triggered a massive calving episode upon reaching the end of the glacier, or glacier terminus.
Unlike calving events shown in movies, which often depict a single chunk of ice breaking and falling into the water below, this massive calving episode recorded 25 consecutive events over two hours. The largest single calving event during this episode was also one of the largest of the 125 total calving events that the researchers captured during their 13-day field campaign in the SKK region.
In the study, researchers documented a direct causal relationship between lake drainage and calving activity, concluding that disturbances from upstream drainage events can propagate downstream without dampening and directly affect calving events at the glacier terminus.
More melting, more downstream risk
The Greenland ice sheet alone is responsible for 20% of current global sea level rise. Jonathan Kingslake, a glaciologist at Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School, told GlacierHub that "while general statements about the frequency and magnitude of similar events may be hard to make, there is probably going to be more drainage and melting in the future."
The rate of melting in Greenland, which is nearly seven times faster than it was 30 years ago, creates alarming risks for coastal communities that are highly vulnerable to destructive flooding events and saltwater intrusion. Arctic ice sheet loss may also destroy vital wildlife habitats and disrupt marine ecosystems in the region.
While there are no numerical estimates of how this process chain will affect total glacier loss, drainage and calving events may occur more frequently because of climate change.
"There will generally be more melting on glacier surfaces where they're in contact with the atmosphere, or at the sides where they're in contact with the ocean," Kingslake said. "The ocean is warming, so its warmer currents cause ice sheet loss as a secondary element." As rising temperatures accelerate ice melt, the potential increase in massive calving events will only exacerbate the irreversible loss of the Greenland ice sheet.
Publication details
Adrien Wehrlé et al, Velocity and calving response of a major Greenland ice stream to a lake drainage event, Nature Geoscience (2025). DOI: 10.1038/s41561-025-01858-2
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Citation: Massive calving episode in Greenland may foreshadow more rapid ice sheet loss (2026, July 7) retrieved 14 July 2026 from https://phys.org/news/2026-07-massive-calving-episode-greenland-foreshadow.html
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