Transport and transformation pathways of coastal methane cycling

Coastal zones and marginal seas are dynamic interfaces between land and ocean, characterized by highly heterogeneous biogeochemical processes that can act as both sources and sinks of methane (CH4). 

While significant progress has been made in quantifying vertical CH4 fluxes, key uncertainties remain in understanding methane sources, sinks, and horizontal transport across the land to sea continuum. Processes such as water column CH4 oxidation and lateral inputs from rivers and submarine groundwater discharge (SGD) are still poorly constrained. 

This thesis aims to improve coastal CH4 budgets by resolving these processes across different water types, using field data collected from different regions. The work focuses on quantifying CH4 oxidation in the water column, assessing horizontal CH4 exports from land to coast, and evaluating its relative importance compared to air–sea exchange. 

Together, this research provides new insights into CH4 dynamics in coastal systems and contributes to a more complete understanding of their role in future greenhouse gas emissions. 

Opponent: Henry Lok Shan Cheung, Department of Marine Sciences