IAP-25-070

Isotopic window into past & future of peatland methane emissions (ISOPEAT)

The global carbon cycle is undergoing rapid and unprecedented change, with feedback between the biosphere, atmosphere, and hydrosphere driving climate instability. Wetlands, and particularly peatlands, occupy a pivotal position in this cycle. They represent one of the largest terrestrial stores of organic carbon while simultaneously acting as the planet’s dominant natural source of methane (CH₄), a potent greenhouse gas. Yet, despite their recognised importance, the long-term controls on peatland methane emissions—and their response to climate variability—remain incompletely understood.

Modern observations reveal that methane fluxes from peatlands are highly sensitive to temperature, water-table position, and substrate availability. However, our ability to predict their future behaviour is constrained by the limited temporal scope of instrumental data.

While paleoenvironmental archives offer a powerful means of overcoming this limitation, peat deposits have not yet been fully exploited for this purpose. Recent studies have highlighted the potential of isotopic analyses of biomarkers—particularly archaeal membrane lipids—to shed light on past methane production and oxidation dynamics. However, the interpretation of these proxies still relies on sparse calibration data.

This PhD project will integrate field measurements, laboratory experiments, palaeo-record analyses, and process-based modelling to refine our understanding of methane cycling in peatlands across timescales. Objective 1 will quantify in situ relationships between environmental variability, methane fluxes, and isotopic signatures across contrasting peatland settings in Scotland (e.g. Flanders Moss, with access facilitated by Prof. Jens-Arne Subke) and potentially in Canada (through collaboration with Dr Peter Douglas). Objective 2 (collaboration with Dr. Adrian Bass) will conduct controlled microcosm experiments to isolate microbial and physicochemical controls on isotopic fractionation. The mechanistic insights gained from these studies will inform Objective 3 (collaboration with Dr. Wenxin Zhang), which applies the process-based ecosystem model LPJ-GUESS, coupled with a peatland methane module, to simulate biogeochemical dynamics through time. Model inputs will be constrained by proxy data from peat cores, enabling the reconstruction of past CH₄ emissions and assessment of their climatic and ecological drivers.

Ultimately, this work will bridge modern and paleo perspectives, strengthening the representation of peatlands in carbon cycle models and improving predictions of their feedback in a warming world.

Key objectives:
i) Quantify in situ relationships between climate variability, methane fluxes, and the isotopic composition of diagnostic biomarkers in contrasting peatland settings.

ii) Conduct controlled laboratory experiments to test mechanistic links between environmental parameters, microbial processes, and isotopic signatures.

iii) Integrate these findings with process-based modelling (LPJ-GUESS) to reconstruct past CH₄ emissions and identify their dominant climatic and ecological controls.

The student will receive comprehensive training in both field and laboratory techniques spanning modern, experimental, and paleoenvironmental research. Core skills will include the quantification of greenhouse gas fluxes using chamber and laser-based systems, analysis of peat and porewater chemistry, and controlled microcosm experiments simulating environmental variability. A strong analytical component will focus on gas chromatography–isotope ratio mass spectrometry (GC–IRMS) for compound-specific isotope analysis (CSIA) of biomarkers, with potential extension to high-resolution Orbitrap mass spectrometry for molecular-level characterisation. Together, these methods will equip the student with cutting-edge expertise in biogeochemical and isotopic approaches to studying carbon cycling across timescales. The successful candidate will have access to the full suite of analytical facilities and instrumentation available through the supervisory institutions and collaborators.

Year 1

Their will be some degree of flexibility of the research plan based upon discussions and preliminary work in the first few months of the PhD, but roughly we anticipate a potential timeline as follows:
1. Literature review, research gap exploration.
2. Sites selection.
3. Initial controlled laboratory experiments.

Year 2

1. In situ experiment in selected sites.
2. Analytical development on compound-specific isotope analysis.
3. First manuscript production based on analytical development.

Year 3

1. Completing In situ experiment in selected sites.
2. Manuscript production on controlled laboratory experiments & CSIA
3. Complete CSIA on peat core samples and integrate results with modelling outputs.

Year 3.5

1. Manuscript production on In situ experiments
2. Manuscript production on past CH₄ emissions simulated by LPJ GUESS
3. Thesis submission and viva preparation

This project provides an exceptional opportunity for interdisciplinary training in field ecology, experimental biogeochemistry, and advanced isotopic and molecular analyses, equipping the successful candidate with a unique skill set highly applicable across environmental science, analytical chemistry, and climate research careers.

The candidate will work closely with all supervisors and collaborators. At the University of Glasgow, Dr Marc-Andre Cormier will oversee project direction, development, and overall progress, providing training in compound-specific isotope analysis (CSIA) of biomarkers within the Biomarkers for Environmental and Climate Science (BECS) laboratory. Dr Adrian Bass, also at Glasgow, will provide training in greenhouse gas flux measurements and advanced analytical techniques within the University’s Carbon Analytical Suite. At the University of Stirling, Prof Jens-Arne Subke will offer additional supervision and expertise in carbon cycle dynamics and peatland greenhouse gas fluxes, as well as facilitating field access to the long-term monitoring site at Flanders Moss and associated research infrastructure. Dr Peter Douglas (McGill University) will act as international collaborator, contributing his expertise in isotope geochemistry, compound-specific biomarker analysis, and peatland microcosm systems, while coordinating, if required, access to complementary Canadian peatland field sites. Dr Wenxin Zhang, based at Glasgow, a core LPJGUESS modelling team member, will supervise student to run LPJ GUESS model and estimate the past CH4 emissions using reconstructed climate data from proxy data from peat cores.

The student will benefit from access to state-of-the-art analytical facilities at BECS and, where required, at the Scottish Universities Environmental Research Centre (SUERC), including gas chromatography–isotope ratio mass spectrometry (GC–IRMS) and high-resolution Orbitrap mass spectrometry. In addition, the candidate will have access to postgraduate training courses, including LPJ GUESS modelling course, at the University of Glasgow, and to the extensive IAPETUS doctoral training programme, providing opportunities to develop both specialist technical expertise and a broad range of transferable research and professional skills.