- Address global uncertainty in future atmospheric methane concentrations.
- Apply state-of-the-art technology to provide a step change in our capability to measure methane emissions from their largest natural source.
- Strong support from industry case partners and a wide international network of experts in advanced sensor technologies.
Wetlands represent the largest and most uncertain global methane source (Kirschke et al., 2013). With atmospheric methane concentrations now increasing rapidly after a period of stabilization (1999 and 2006; Nisbet et al., 2014), the quantification of current and future emissions from wetlands represents a core challenge to climate science. However, the tools needed to effectively measure methane emissions are unavailable. Eruptions of gas bubbles from wetlands provide an important transport pathway of methane to the atmosphere. But the spatio-temporal complexity of such events means that they cannot be effectively quantified using traditional field based approaches (Stamp et al., 2013); gas emerging from hot spots during hot moments (McClain et al., 2003).
This project will revolutionize the in situ measurement of bubbling events through the development and application of a real-time monitoring network (Krause et al., 2015). The approach will combine novel fibre optic acoustic technology (Conway and Mondanos, 2015), integrated with traditional point source methods (Baird et al., 2004, Stamp et al., 2013) and driven through machine learning data analysis. The technique offers unrivalled capability to measure individual bubbles movements (Leighton, 2017) over transects kilometres in extent.
The project will apply the approach to assess the stability of large accumulations of methane locked deep within wetlands (Glaser et al., 2004, Comas et al., 2005) to seismic activity. It will determine the extent to which earthquakes provide previously overlooked triggers of methane emissions within seismically active tropical wetlands. The network will i) characterize pore scale behaviour of biogenic gas bubbles necessary for the development and evaluation of state-of-the-art modelling approaches (Ranmirez et al., 2015), ii) quantify methane losses and their spatio-temporal dynamics to centennial disturbance events, and iii) provide the technological foundation to develop an international network of stations across the broad range of wetland classes and climate regimes that drive methane fluxes (Turetsky, 2014). The integration of this approach within flux tower networks, such as the ABoVE programme within northern latitudes, will constrain land surface models and the determination of global methane budgets (Kirschke et al., 2013).
The iDAS system is able to record the acoustic signal continuously (listen) along a fibre optic cable kilometres in length. Bubbles that transport methane make a sound because they vibrate, with the tone of the bubble indicating its size (Leighton, 2017). By listen for these bubbles it is therefore possible to determine the number of individual bubbles that are transported and the size of those bubbles. This technique has been applied in ocean science at the point scale using hydrophones. The iDAS capability now offers the opportunity to measure across a landscape. This will be combined with artificial seismic events introduced within the laboratory and within field sites to mimic natural eruptions in response to earthquakes. The approach will be integrated with traditional moisture probes, geophysics, chamber based and open path measures of methane gas fluxes.
Training and Skills
In addition to the CENTA2 training, you will integrate within the active and diverse Physical Geography research group and national and international collaborative and training networks lead by the supervisory team. This ambitious, supportive environment provides you with all the essential training necessary to undertake the PhD, in addition to the diverse learning environment reinforced by regular seminar series and fortnightly water sciences and ecological discussion groups. The international networks provide purpose built connections and the financial mechanisms for extended visits to international partners from Northern Canada to New Zealand, for training or method implementations.
There is substantial flexibility in the direction in which the project can take over the 3 years of the PhD programme, supported by a supervisory team with an extensive breadth and depth of expertise in wetland biogeochemistry, hydrology, ecology and advanced sensor networks. The below provides a brief suggestion which will be developed by the successful student in line with their own interests and expertise.
Year 1: Laboratory experiment assessing the acoustic signature of bubbles from point measurements. Quantification of the capability and accuracy of the acoustic technique for the measurement of biogenic bubble releases within wetland environments. Preparation of first PhD publication for submission. Training in the application of the iDAS system for field deployment. Training applied in a UK wetland for preliminary data collection.
Year 2: Development of the workflow protocols to process the ‘big data’ generated, formulating in-line data protocols for the iDAS system (spatiotemporal measurement frequencies, data analysis and storage algorithms; potentially utilizing machine learning). Placement and advanced training undertaken within Silixa on iDAS data analysis. Preparation of second paper for publication and completion of first submission.
Year 3: Application of the iDAS system within a tropical wetland within Vietnam to monitor natural small scale methane eruptions followed by simulation of localised seismic events to monitor scale and releases. Research to be undertaken in collaboration with partners in the international network linked to smart high-frequency environmental sensing. Completion of two final PhD papers in preparation for submission.
Throughout this project there will also be the opportunity contribute to additional research activities being undertaken within the community, to support the in the submission of additional research papers associated with advanced sensor networks and wetland biogeochemistry.
Partners and collaboration (including CASE)
This is a CASE PhD studentship with direct financial and indirect training support provided by Silixa (https://silixa.com) who have developed the acoustic technology for application principally within the oil, gas and mining sectors. You will join a strong team of PhD students and postdoctoral researchers within the university who are working with fibre optic measurement systems to tackle environmental grand challenges. Further, the project aligns closely with the global network lead by the University of Birmingham in applying smart high-frequency environmental sensor networks such as this for quantifying non-linear hydrological process dynamics across spatial scales.