Freshwater methane emissions – what are the learnings from repeated measurements on multiple boreal and subarctic lakes?

Open freshwaters appear to be the second largest natural source of methane (CH4) globally, but the present data is dominated by short measurements (30 min to 24 h). Moreover, such measurements were rarely repeated regularly which makes overall data and interpretations of flux regulation uncertain. For example, recent results indicate that periods with high temperatures or passing low pressure events can greatly influence fluxes and thereby it is unclear how representative previous data are. Consequently, we lack the information needed to build predictive models of CH4 emissions in different types of lakes and under different conditions. This presentation summarizes results from repeated spatially distributed CH4 flux measurements over full growth seasons to years, in multiple lakes in Sweden at different latitudes, and having varying characteristics in terms of nutrient and organic carbon concentrations, and basin morphometry. Questions regarding differences among lakes, factors regulating emissions, and possibilities to predict methane emissions from lakes will be in focus.