Interpreting the seasonality of atmospheric methane
The amount of methane (CH4), a greenhouse gas with a global warming potential 80 times that of CO2 on 20-year time scales, has been growing in Earth’s atmosphere during the last decade, and scientists disagree about which methane sources and sinks are responsible for the growth. One clue into understanding methane’s sources and sinks is their seasonality – their month-to-month cycles that happen every year. Measurements of atmospheric methane taken at the Earth’s surface and using satellite instruments show a steep increase each summer in the Northern Hemisphere that is not replicated when methane is simulated in a global chemical transport model, indicating missing information about source and sink seasonalities. To investigate, we use the GEOS-Chem global chemical transport model to simulate 24 representations of methane’s largest source, emissions from wetlands, and 22 representations of its largest sink, chemical loss by the hydroxyl radical (OH). We find that OH is unlikely to cause the summer increase and model bias. Instead, global wetland emissions drive the summer increase through their amount, spatial distribution, and seasonal cycles. We suggest that these characteristics are linked to the underlying mechanisms determining wetland area and methane production in wetland models. The results unveil the role of global wetlands in driving methane’s seasonality and inform analyses of methane’s long-term trends.

Virtual Meeting Info:

https://us02web.zoom.us/j/83318805931?pwd=Y0hMelE3YjQ2SEMyRXYzL2lTdHlXdz09

Meeting ID: 833 1880 5931
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