A new study reveals how responsive the Greenland ice sheet is to climate change – more so than models predict. Methane has been detected at retreating glacier margins worldwide, but this is the first time that a study has investigated the margin of an entire ice sheet.
In the new paper, an international collaboration including Charles University, Czechia, and University of Oulu, Finland, presents evidence linking widespread methane (CH4) release – a potent greenhouse gas – from beneath the Greenland Ice Sheet to an episode of warming around 4,000 years ago, known as the Holocene Thermal Maximum.
The scientists collected samples from a 2000 km-long transect of the western margin of the Greenland Ice Sheet and used stable isotope analysis and radiocarbon dating to constrain the origin and age of the methane exported by emerging subglacial meltwater. They found the methane was 1500-4500 years old, produced biologically by anaerobic microbes that metabolise decaying organic matter in sediments beneath the ice sheet, where oxygen is limited.
The implication is that the ice sheet retreated significantly inside its present margins after the last ice age, allowing boreal and tundra vegetation to grow in the newly exposed areas. This was subsequently overridden by the readvancing ice in the following colder period. The retreat suggests a highly dynamic ice sheet, one that is far more sensitive to climate change than previously thought, with clear implications for its future behaviour.
“Our study reveals startling insights into just how responsive the Greenland ice sheet is to climate change. That it abruptly retreated to a configuration much smaller than present under levels of Arctic warming on a par with that ongoing today, is a bleak reminder of its future committed loss to global sea-level rise and coastal flooding, if we can’t get our act together to curb greenhouse gas emissions. The ultimate irony”, says co-author, professor Alun Hubbard from the University of Oulu, “is that as it retreats, the ice sheet itself further contributes to those methane emissions.”
In recent years, international scientific discussion has increasingly highlighted the so-called hidden methane phenomenon: evidence that methane reservoirs beneath the glaciers may be released as ice retreats. Researchers warn that they may represent a climate-warming feedback mechanism. At present, these emissions are not significant at the global scale, but that can change as rates of deglaciation increase.
“Our findings highlight the role of these recent ice margin fluctuations on subglacial carbon cycling. The results are highly relevant for the global methane budget assessments. Increased ice sheet melting will lead to greater subglacial connectivity and potentially amplified methane transport in the future, not only from the Greenland Ice Sheet but also from the Antarctic Ice Sheet, where the organic matter reserves are much larger than in the Arctic”, says Jade Hatton, the lead author of the study, at Charles University.
The findings were published in Nature Geoscience on 5 May 2026: Mid-Holocene retreat of the Greenland Ice Sheet indicated by subglacial methane release.
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