Melting Svalbard glaciers are flushing ancient methane into the atmosphere, study finds

Meltwater rivers draining glaciers on the Norwegian archipelago of Svalbard are carrying far more methane into the atmosphere than previously documented, according to a study published Tuesday in Nature Communications. Researchers who sampled 19 glacier-fed rivers across the central part of the archipelago found that every one of them was releasing methane well above the level expected from simple contact with the air, with peak concentrations reaching 425 times atmospheric equilibrium.

The gas is not being produced by microbes living under the ice, the dominant source considered in most prior Arctic methane research. Carbon isotope analysis, together with traces of ethane and propane that accompany the methane, points instead to a geological origin: ancient organic matter locked in shale bedrock for millions of years, now being flushed loose as glacial meltwater works its way down through cracks and crevasses to the rock below.

The finding matters because it identifies a mechanism that could accelerate as the Arctic continues to warm. Glaciers that are melting more each summer send more water to their beds, and that water, in turn, appears to liberate more gas from the rock underneath. "The amounts reported here are small compared with human-caused emissions from fossil fuels, farming and waste," said Gabrielle Kleber, the study's lead author and a researcher at the iC3 Polar Research Hub at UiT The Arctic University of Norway in Tromsø. But the pathway, she and her co-authors argue, represents a natural feedback loop that has been largely absent from climate models.

What the sampling found

The team, which also included Leonard Magerl and Silje Waaler of UiT, collected 148 water samples from the 19 rivers over multiple field seasons, deliberately choosing glaciers that sat on different types of bedrock and had different basal ice conditions. Waaler said the design was meant to capture "many different glaciers, across a range of rock types and ice conditions," rather than generalizing from a single site.

Combining the concentration measurements with river discharge data, the researchers estimated that Svalbard's land-terminating glaciers are releasing somewhere between 182 and 368 tonnes of methane into the atmosphere each year, a range that reflects uncertainty in how the measurements scale up across the region. To understand why some rivers carried far more gas than others, the team paired the chemistry with ground-penetrating radar surveys and thermal modeling of the glacier beds. The clearest signal, they found, was where thawed, water-connected ice sat directly above organic-rich shale: those combinations produced the highest methane readings by a wide margin. "The temperature at the glacier base is an important piece of the puzzle," Kleber said, since a bed frozen solid to the rock beneath it blocks the meltwater pathways that let gas escape.

Building on earlier fieldwork

The new survey builds directly on a smaller body of work by the same research group. In 2023, a study in Nature Geoscience led by Kleber, then working with researchers at the University of Cambridge, surveyed more than 100 groundwater springs across Svalbard and estimated that they could be releasing over 2,000 tonnes of methane annually — a figure the team said was roughly equivalent to 10 percent of methane emissions from Norway's entire oil and gas industry. A follow-up published last year in Biogeosciences tracked methane through an entire melt season at a single glacier, Vallåkrabreen, and first described the process researchers have since taken to calling "glacial fracking": meltwater acting like a natural hydraulic system, forcing its way through fractures in bedrock and carrying trapped gas up and out.

What distinguishes the new paper is scale and mechanism. Rather than a single site or a network of static springs, it covers 19 actively draining glacier rivers and links the variation between them to measurable properties of the ice and the rock beneath it — a step toward predicting, rather than simply documenting, where and when the emissions will be largest. Cambridge researchers involved in the earlier work had already flagged glacial methane as a gap in the global methane budget; the Svalbard team's newer findings give that gap a physical explanation rooted in geology rather than biology.

"The amounts reported here are small compared with human-caused emissions from fossil fuels, farming and waste."

Who is watching this closely

The immediate audience for the findings is the community of scientists who build global methane budgets — the accounting exercises that track how much of the gas enters and leaves the atmosphere from natural and human sources, and that underpin projections used by the Intergovernmental Panel on Climate Change. Glacial methane release from bedrock has not featured prominently in those budgets, and the Svalbard data offer a rare quantitative handle on a source that is otherwise difficult to measure directly. Arctic and glaciological researchers more broadly have an interest as well, since the geological conditions described in the paper — organic-rich shale beneath ice that periodically or permanently thaws at its base — are not unique to Svalbard. Similar rock types are found beneath glaciers in parts of Arctic Canada, Greenland and Russia, though the authors caution that no equivalent survey has yet been done in those regions to confirm the same process is at work there.

Policymakers tracking the pace of Arctic change also have reason to note the result, less because of the volume of gas involved — which the authors are explicit is modest next to fossil-fuel and agricultural emissions — than because it adds one more warming-driven mechanism that current climate models do not explicitly account for, alongside better-known feedbacks such as permafrost thaw and reduced sea-ice reflectivity.

Caveats and what comes next

The authors are careful to note that the relationship between warming and methane release is not simply linear. Some retreating glaciers, as they thin, can actually become more frozen to their beds rather than less, which would reduce rather than increase the flushing effect the study describes; the outcome, they write, depends on the specific interplay of ice thickness, basal temperature and the geology underneath. "Future methane release will depend on both geology and glacier change," Kleber said, underscoring that the finding is not a simple prediction of ever-rising emissions but a description of a mechanism whose strength varies by location.

The research, funded through the Research Council of Norway's Centres of Excellence scheme, was limited to central Svalbard, and the authors say the next step is determining how widespread the same geological pairing — thawed glacier beds atop organic-rich shale — is elsewhere in the Arctic and in mountain glacier systems such as the Himalayas, where comparable bedrock exists but no comparable survey has been conducted. Coverage of the release noted that answering that question will likely require years of additional fieldwork, given the remoteness and logistical difficulty of sampling glacier rivers across the wider Arctic. Until then, the Svalbard figures stand as the most detailed estimate to date of a methane source that, by the researchers' own account, remains small in absolute terms but poorly understood in how it might change as the region continues to warm.