Researchers sampled 26 meltwater streams across the entire western margin of the Greenland Ice Sheet (GrIS). They found pervasive, biogenic methane (CH₄) dissolved in supersaturated subglacial meltwater. Radiocarbon dating showed the CH₄ is 1.5–4.4 thousand years old (roughly 1500–4500 years before present).

This methane was produced by methanogenic archaea (microbes) breaking down organic matter under anoxic (oxygen-poor) conditions beneath the ice. The ages align with the Holocene Thermal Maximum (roughly 11–5 ka BP), a warmer period when the Greenland Ice Sheet was smaller than today. Proglacial areas accumulated organic matter (soils, vegetation), which later advancing ice overrode, providing the substrate for subglacial methanogenesis.

Methanogenic archaea (also called methanogens) are a specialized group of anaerobic archaea that produce methane (CH₄) as a byproduct of their energy metabolism. They are the only known organisms capable of methanogenesis and play a critical role in the global carbon cycle, especially in oxygen-free (anoxic) environments.

Domain: Archaea (not bacteria). They have distinct cell membranes (ether lipids), ribosomes, and metabolic pathways that differ from bacteria.

Strict anaerobes: Oxygen is toxic to them. They thrive in environments with no or very low oxygen, such as wetlands, rice paddies, ruminant digestive tracts, marine sediments, landfills, and subglacial sediments.

Energy metabolism: They are chemolithotrophs or chemoorganotrophs that generate energy by converting simple carbon compounds into CH₄. This process is their primary (often only) way to obtain energy.

Main Methanogenesis Pathways

1. Hydrogenotrophic (CO₂-reducing): The most widespread.
   CO₂ + 4H₂ → CH₄ + 2H₂O
   Uses hydrogen (H₂) or formate as electron donors.
2. Acetoclastic (acetate-splitting): Common in freshwater sediments.
   CH₃COOH (acetate) → CH₄ + CO₂
3. Methylotrophic: Uses methylated compounds (methanol, methylamines, dimethyl sulfide, etc.).
   Example: 4CH₃OH → 3CH₄ + CO₂ + 2H₂O

Some methanogens can also use other substrates like alcohols or even methoxylated aromatic compounds from lignin.

They use unique coenzymes such as coenzyme M (CoM), coenzyme B, tetrahydromethanopterin (H₄MPT), and factor F₄₂₀ (which gives some a greenish fluorescence).

In the Greenland Ice Sheet studies (including the recent 2026 Nature Geoscience paper), sequences from Methanosarcinales and Methanomicrobiales are frequently detected in subglacial meltwater.

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Mid-Holocene retreat of the Greenland Ice Sheet indicated by subglacial methane release

Mid-Holocene retreat of the Greenland Ice Sheet indicated by subglacial methane release is the title of a research article published on May 5, 2026, in Nature Geoscience.

Methane (CH₄) emissions occur at glacier margins globally, with subglacial CH₄ production identified beneath the Greenland Ice Sheet (GrIS). Researchers extensively sampled 26 meltwater streams across the entire western margin of the GrIS. They found pervasive, biogenic CH₄ (produced by microbes) dissolved in supersaturated subglacial meltwater. Radiocarbon dating revealed the methane’s age as 1.5–4.4 thousand years before present (ka BP).

These ages indicate that the organic matter fueling subglacial methanogenesis (by methanogenic archaea under anoxic conditions) accumulated in proglacial areas (soils, tundra vegetation) when the ice sheet was smaller than today during the Holocene Thermal Maximum (~11–5 ka BP). Subsequent ice readvances overrode this carbon-rich material, enabling ongoing microbial CH₄ production.

Ice sheet dynamics: The findings support greater mid-Holocene retreat (and subsequent readvance) of the GrIS than some models previously suggested. This points to higher sensitivity to climate warming.

Current and future CH₄ flux: A continuum degradation model estimates that western Greenland’s subglacial organic matter could sustain CH₄ production for another 200 years. The lateral flux from land-terminating sectors is estimated at **715 tonnes per year** (range 481–1,020 t/yr).

Broader context: Subglacial carbon cycling and CH₄ release are relevant to glacial environments worldwide. Increased melting could enhance subglacial connectivity and methane transport in the future

The team (led by researchers including J.E. Hatton, A. Stehrer-Polášková, and M. Stibal from Charles University, Czechia, with international collaborators) used:

• Sampling along a ~2,000 km transect of the western GrIS margin.
• Stable isotope analysis.
• Radiocarbon (¹⁴C) dating of the CH₄.

This distinguishes biogenic (microbial) origins from thermogenic or hydrate sources (which would lack modern radiocarbon).

The paper builds on earlier site-specific studies (e.g., at Leverett or Isunnguata Sermia glaciers) by demonstrating the phenomenon is widespread. Popular summaries appear on Phys.org, University of Oulu, and other sites. Access to the full text may require institutional login or purchase via Nature.com.

Published: Nature Geoscience 

DOI: 10.1038/s41561-026-01976-5

Provided: Charles University

Authors: J. E. Hatton, 
A. Stehrer-Polášková, 
P. A. Píka, 
M. H. Garnett, 
P. Klímová, 
L. C. P. Wentzel, 
J. D. Žárský, J. Trubač, 
S. Arndt, 
A. Hubbard, 
J. C. Yde, 
J. R. Hawkings, 
E. L. Doting, 
J. G. Murphy, 
G. Lamarche-Gagnon, 
J. L. Wadham, 
S. E. Sapper, 
J. R. Christiansen, 
C. J. Jørgensen & 
M. Stibal

Abstract

Methane (CH₄) emissions have been detected at glacier margins globally, with subglacial CH₄ production identified beneath the Greenland Ice Sheet. Despite its potential role in carbon cycling, an assessment of the sources, production pathways and prevalence of subglacial CH₄ export is lacking. Here we report on extensive sampling of 26 meltwater streams across the entire western margin of the Greenland Ice Sheet, revealing a radiocarbon age of 1.5–4.4 thousand years before present for pervasive, biogenic CH₄ laterally transported by emerging subglacial supersaturated meltwater. These ages corroborate a smaller-than-present Greenland Ice Sheet during the Holocene Thermal Maximum (11–5 thousand years ago before present), stimulating proglacial organic matter accumulation, which was then overridden by subsequent glacial advance. Applying a continuum degradation model, we demonstrate that western Greenland’s subglacial organic matter can support CH₄ release for another 200 years, with a lateral flux of 715 (481–1,020) tonnes per year from its land-terminating sectors. We highlight the pertinence of subglacial carbon cycling to the release of CH₄ from all glacial environments globally, and a dynamic sensitivity of the Greenland Ice Sheet not yet fully realized in ice sheet models, via the isotopic assessment of subglacial CH₄.