GLaME 2026 Summer

This project will make high-resolution measurements of dissolved CH4 partial pressure in surface waters of all five Great Lakes on three new research cruises, using a novel underway system that calibrates a Gas Membrane Contactor (GMC) against equilibrator and discrete vial measurements. The new measurements will be merged with existing data collected using a similar system on previous cruises, yielding a CH4 archive that captures the seasonal cycle and covers potential hotspots associated with river discharge and gas wells. This archive will be used to train machine learning models to map CH4 disequilibrium between the lake surface and air, allowing the lake-atmosphere CH4 flux to be calculated at high resolution across the Great Lakes. We will also conduct incubation experiments and stable isotope analyses to construct mixed layer CH4 budgets for each Great Lake, and employ radiocarbon fingerprinting to trace the contribution of fossil CH4 through the Lake Erie water column. These analyses will allow us to partition the roles of in situ aerobic methanogenesis, leakage from oil and gas wells, and other external CH4 sources (sediments, runoff), in driving CH4 emissions.