Paleoclimate
Why LGM methane needs a bigger wetland collapse
Open access · cc by · source: Europe PMC
Ice-core CH4 and isotopes imply about a 50% source drop at the LGM; process models underpredict both concentration and isotopic shifts.
Study at a glance
- Design
- Computational / modelling — MCMC inversion of LGM vs preindustrial CH4 and isotopes in a three-box model
- N
- Ice-core constraints and Earth-system flux priors; not an observational sample N
- Population
- Atmospheric methane budget from LGM to late preindustrial (ice-core constrained)
- Outcome
- Required source reductions and isotope shifts poorly matched by process models
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
CH4 rose from 375 to 680 ppbv while δ13CH4 fell from −43 to −48‰. Standard LGM fluxes give 447 ppbv and almost no isotope shift. Leaf discrimination adds only ~0.6‰. Posterior wetlands must fall more than models simulate; geologic and fire sources also matter.
Methodology
Authors nested Hopcroft et al. Earth-system methane budgets in a three-box isotope model, added leaf-δ13C and chlorine sinks, then used MCMC to invert LGM versus preindustrial ice-core CH4, δ13C, and δD.
Limitations
High-latitude peat and CH3Cl sources remain poorly represented; a 54 Tg/yr modern geologic source cannot fit the LGM reduction; Cl from extra LGM sea salt is not in the model.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Ice-core CH₄ and isotopes are inversion targets, not a flux measurement. LGM to preindustrial methane rose from 375 to 680 ppbv while δ¹³CH₄ fell from −43 to −48‰. Standard Earth-system LGM fluxes produced 447 ppbv and almost no isotope shift; a Bayesian three-box inversion required a larger wetland collapse than models simulate, with geologic and fire sources still in play.
Evidence for the claim as stated.
Measuring organics in a core, inverting published ice-core CH₄, and compositing modelled snowfall at core sites are three different uses of 'ice core.' The Bouvet paper is laboratory chemistry on ice; the methane paper is a box-model inversion of existing core time series; the circulation paper is not a core study. Combining them into one 'what ice cores show' paragraph would be a category error.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Measuring organics in a core, inverting published ice-core CH₄, and compositing modelled snowfall at core sites are three different uses of 'ice core.' The Bouvet paper is laboratory chemistry on ice; the methane paper is a box-model inversion of existing core time series; the circulation paper is not a core study. Combining them into one 'what ice cores show' paragraph would be a category error.
Related papers in this topic
Same topic cluster — not a recommendation engine.