Lake drainage triggers fast calving pulse on Greenland

supraglacial lake – A study of Sermeq Kujalleq (Jakobshavn glacier) shows that when two surface lakes drained in July 2022, the surge of meltwater raced to the glacier’s lowest depths within hours—lubricating the ice stream, accelerating flow by more than 16 km downstream in four

For four hours in July 2022, the surface of Greenland’s Jakobshavn glacier didn’t just change—it surged. And when that speed-up finally reached the glacier’s end, the ice responded with a burst of calving that unfolded as a chain of events, not a single break.

Last November. a study led by Adrien Wehrlé. a researcher in the department of geography at the University of Zürich in Switzerland. followed what happened when two supraglacial lakes drained into Sermeq Kujalleq (SKK) in the Kangia icefjord. Supraglacial lakes are temporary meltwater ponds that form and accumulate in depressions on the surface of glaciers and ice sheets.

SKK is also known as the Jakobshavn glacier. It’s a large. rapidly retreating outlet glacier on the Greenland ice sheet—and among the world’s fastest moving and most active ice streams in West Greenland. Each year, it discharges more than 50 gigatons of ice into the ocean. In the study. researchers used satellite and terrestrial radar observations to examine the glacier’s response to the drainage of two lakes in July 2022.

The timing was stark. Between July 21 and 24, two supraglacial lakes positioned 13 km south of SKK and 25 km from the glacier’s edge released a catastrophic surge of fast-flowing meltwater. That pulse propagated all the way to the glacier’s lowest depths.

The mechanism the researchers documented follows a grim logic. A drainage event sends a sudden pulse of meltwater to the bottom of the glacier. lubricating the ice and triggering faster flow. The accelerated ice then destabilizes the glacier edge. forcing open pre-existing cracks at the glacier front and setting off a cascade of calving.

In this case, the July drainage event produced a subglacial flood at the base of the ice stream. Lubrication at the bottom helped rapidly accelerate ice flow. Under “regular” conditions, SKK’s flow speed is around 7 km per year. But the lake-driven acceleration created a surface speed-up pulse that traveled more than 16 km downstream within four hours.

The speed-up was described as roughly a walking pace—around 2.5 miles per hour—and it lasted for 24 hours. When the accelerated flow reached the glacier terminus, it triggered a massive calving episode.

Unlike calving scenes often shown in movies—where a single chunk breaks away—this episode unfolded repeatedly. Researchers recorded 25 consecutive calving events over the span of two hours. The largest single calving event during the episode was also among the largest of the 125 total calving events the team captured during their 13-day field campaign in the SKK region.

The study’s findings were not just observational. Researchers were able to document a direct causal relationship between lake drainage and calving activity. concluding that disturbances from drainage events upstream can propagate downstream without dampening and directly impact calving events at the terminus.

That matters because the broader Greenland system is changing quickly. The study notes that rising temperatures and increased melting can cause larger lakes, which may raise the frequency and magnitude of drainage events—further degrading glaciers and contributing to sea-level rise.

Glaciologists have long linked meltwater to glacier dynamics, but the stakes now include how often such linked processes might occur. The Greenland ice sheet alone is responsible for 20% of current global sea level rise. Jonathan Kingslake. a glaciologist at Lamont-Doherty Earth Observatory. 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.”.

Melting in Greenland is nearly seven times faster than it was 30 years ago. That acceleration brings alarming risks for coastal communities, which are highly vulnerable to destructive flooding events and saltwater intrusion. It also threatens Arctic ice sheet loss could destroy vital wildlife habitats and disrupt marine ecosystems.

Even without a numerical estimate for how this specific process chain changes total glacier loss. the study points to what comes next. Drainage and calving events may occur more frequently as climate change intensifies melt. Kingslake said 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.” He added that “the ocean is warming. so its warmer currents cause ice sheet loss as a secondary element.”.

Put simply: as rising temperatures accelerate ice melt, the potential for more massive calving events can worsen the already irreversible loss of the Greenland ice sheet.

When the lakes drained in July 2022. the glacier’s response moved fast enough to reach its lowest depths and reorganize flow—then expressed that reorganization at the terminus through a burst of 25 consecutive calving events. The question now is how often Greenland’s warming will set that sequence in motion again.

Greenland ice sheet Sermeq Kujalleq Jakobshavn glacier supraglacial lakes lake drainage calving event subglacial flood ice flow acceleration sea level rise glaciology