Methane emissions from inland waters: Quantifying the largest uncertainty in the global methane budget

Project outline

Methane (CH₄) is the second most important greenhouse gas after carbon dioxide, accounting for 35% of the greenhouse gas-driven warming in 2010-2019 relative to 1850-1900¹. Methane emissions continue to increase annually at a rate of 18.1 ppb/yr. Globally, aquatic ecosystems account for approximately half of methane sources, with inland water emissions among the most, if not the most, uncertain worldwide methane source². Sources of uncertainty associated with the methane emissions in inland waters include a poor understanding of how the empirical drivers of emissions change across rivers of varying sizes and stream orders in response to different river flows, river management regimes (e.g. damming), seasonal changes including temperature and light availability, and land use types, which influence nutrient concentrations and in turn, ecosystem metabolism³. Addressing the whole-system drivers of methane emissions across space and time has previous been limited by the absence of large-scale river network data products that include flow data at the reach scale. The recent publication of the global reach-scale, river flow model MERIT-Hydro⁴ and 35 years of associated flow data (GRADES)⁵ now allows for the development of biogeochemical models that track the cascading fluxes and transformations of dissolved constituents such as methane through inland waters worldwide at previously impossible resolutions, enabling local conclusions to be generated as well as global.

Project goals

The primary goal of this research is to use a combined model- and field-based approach to quantify the large-scale (national, continental, and/or global) controls and drivers of methane emissions from inland waters, including rivers, reservoirs, lakes, wetlands, and estuaries, and forecast how emissions will change in the future. The modelling component will rely on the high-resolution hydrological and GIS data products now available as the system backbone, with methane emission mechanisms constrained using a combination of empirical observation field data collected by the student, mechanistic or kinetic data, and machine learning approaches. Field data will include the use of floating greenhouse gas flux chambers installed on rivers and water bodies at strategic sampling points. An interdisciplinary approach will allow the student to develop a project that integrates elements of (1) hydrological modelling, (2) biogeochemical modelling, and (3) climate modelling. The project outcome will be directly relevant to IPCC and Global Carbon Project stakeholders (https://www.globalcarbonproject.org/), as well as local and national governments aiming to meet climate emissions goals.

Benefits

The successful candidate will benefit from inter-disciplinary training in hydrology and aquatic science as part of the River Basin Processes and Management, the Leeds institute of Data Analytics (LIDA) in the School of Geography, and the Priestley International Centre for Climate. Training at Leeds deals fully with the elements described in the Joint Research Centre statement on skills training for research students. PhD students take modules provided by the staff development unit (e.g. starting your PhD, small group teaching) and a 15-week faculty-training course (covering elements such as planning, critical reading and writing, oral presentations, writing research papers). Students present results and receive constructive feedback from peers in a Research Support Group, from colleagues in the River Basins research group, and at a university postgraduate research day. The student will also benefit from being part of water@leeds, the largest interdisciplinary water centre in any UK university, which runs a postgraduate forum.

The nature of the project means that the student will be trained in project specific research methods including literature reviews, fieldwork techniques, laboratory water quality analysis, and modelling/statistics for analysing data, both internally and at external workshops. An additional important part of the training will be to attend national and international conferences to present results and gain feedback. The student will be encouraged to submit papers for publication in international journals during the project.

Applications

The prospective student should have, or expect to receive, a minimum 2.1 BSc and/or MSc degree in an appropriate discipline, and have interests and experience in most, if not all, of the following topics: climate change, hydrology, freshwater ecosystems, computing, the water industry and environmental policy/management. Informal enquiries should be directed to Taylor Maavara at t.maavara@leeds.ac.uk. Further details about postgraduate research degrees at the School of Geography, University of Leeds can be found here.

References

1. Saunois et al. 2020. Earth Syst. Sci. Data 12: 1561-1623
2. Rosentreter et al. 2021. Nature Geosci. 14: 225-230
3. Aho et al. 2021. Limnol. & Oceanog. 66:10
4. Yamazaki et al. 2019. WRR 55:6
5. Lin et al. 2019. WRR 55:8