In a new paper, an international team lead by CryoEco has brought evidence linking widespread release of methane (CH₄) – a strong greenhouse gas – from the Greenland Ice Sheet (GrIS) to a warmer period 9-4 thousand years ago. Methane has been detected at retreating glacier margins worldwide, raising concerns about potential climate feedbacks associated with their widespread retreat, but this is the first time that a study has systematically investigated the whole margin on an entire ice sheet.

We collected samples of glacial meltwater across a transect spanning the entire 2000 km-long western margin of the GrIS and used stable isotope analysis and radiocarbon dating to constrain the origin and age of dissolved CH₄ exported by the meltwater.

The carbon in the CH₄ was found to be between 1500-4500 years old and produced biologically as an end product of organic matter degradation under anoxic conditions. This suggests the ice sheet retreated significantly inside its present margins during the Holocene. Tundra vegetation could grow and accumulate organic matter in the newly exposed areas, which was subsequently overridden by the readvancing ice in the following colder period. The retreat also suggests a highly dynamic ice sheet, one that is more sensitive to climate change than previously thought with clear implications for its future behaviour.

The amount of CH₄ exported and released into the atmosphere is relatively small and not significant globally at the moment, but that can change in the near future with the accelerating deglaciation.

Our findings highlight the role of these recent ice margin fluctuations on subglacial carbon cycling. Despite the relatively small CH₄ export from the GrIS at present, our results are highly relevant for the global CH₄ budget assessments. Increased ice sheet melting will lead to greater subglacial connectivity and potentially amplified CH₄ transport in the future, not only from the GrIS but also from the Antarctic Ice Sheet, where the organic matter reserves are much larger than in the Arctic.

The research was supported by the Czech Ministry of Education as part of the ERC-CZ programme (project LL2004 ‘MARCH₄G’ to Marek).

Hatton JE, Stehrer-Polášková A, Píka PA, Garnett MH, Klímová P, Wentzel LCP, Žárský JD, Trubač J, Arndt S, Hubbard A, Yde JC, Hawkings JR, Doting EL, Murphy JG, Lamarche-Gagnon G, Wadham JL, Sapper SE, Christiansen JR, Jorgensen CJ, Stibal M (2026) Mid-Holocene retreat of the Greenland Ice Sheet indicated by subglacial methane release Nature Geoscience doi:10.1038/s41561-026-01976-5