Periodic Reporting for period 4 - METLAKE (Predicting future methane fluxes from Northern lakes)
Période du rapport: 2021-10-01 au 2022-12-31
Methane is one of the most important greenhouse gases. Yet, the sources and sinks of atmospheric methane are poorly constrained. Recent evidence suggests lakes represent one of the most important methane sources, but it is unclear how representative the available data is. Moreover, the variability in space and time of lake methane flux is also unclear, which hamper development and validation of models. Therefore, current lake methane flux estimates are uncertain, and although we expect changed lake fluxes as feedbacks from climate change, we lack means of quantifying and predicting these feedbacks. Such limited knowledge about one of the largest methane sources is a societal problem, because under the Paris agreement, we need to know present and future emissions of all greenhouse gases as they all affect temperature. We also need to know how the extensive natural greenhouse gas emissions will develop in a warmer climate to design appropriate climate mitigation targets. The society also need more effective methods for measuring greenhouse gas fluxes.
The aims of the project include to better quantify methane emissions from lakes, assess how sensitive these fluxes are to changing environmental conditions, and to develop models to predict future lake methane emissions. The METLAKE studies of how lake methane emissions are regulated, and how sensitive they are to global warming, are important to assess how the fluxes will develop and contribute to the future climate. A key is to generate extensive high-quality flux measurements to map spatiotemporal variability and for developing models that are well-validated relative to real measurements. Other long-term aims, with implications beyond the specific project, is to develop supplementary approaches to measure greenhouse gas emissions for use both in lake studies and more broadly in nature and society.
The aims of the project include to better quantify methane emissions from lakes, assess how sensitive these fluxes are to changing environmental conditions, and to develop models to predict future lake methane emissions. The METLAKE studies of how lake methane emissions are regulated, and how sensitive they are to global warming, are important to assess how the fluxes will develop and contribute to the future climate. A key is to generate extensive high-quality flux measurements to map spatiotemporal variability and for developing models that are well-validated relative to real measurements. Other long-term aims, with implications beyond the specific project, is to develop supplementary approaches to measure greenhouse gas emissions for use both in lake studies and more broadly in nature and society.
The project reached these aims and has generated new knowledge regarding (1) lake methane emissions across space and time, and (2) regarding greenhouse gas emissions and methods for flux measurements in general. To provide some examples regarding lake emissions it was shown that:
- There is a pronounced diel variability in lake methane emissions, typically with higher emissions daytime, that is important to be aware of when extrapolating emissions over time.
- The methane found in lakes can have different sources, including surrounding groundwater in addition to the production in the sediments.
- Phosphorous can be a key regulator of water column methane oxidation.
- With systematic sampling, covering within lake spatial variability, variability over time during all seasons as well as variability among days, and between lakes having different characteristics and in different ecoclimatic regimes, more powerful statistical models of lake methane emissions can be derived with multiple driver variables.
The global lake methane emissions were re-assessed accounting for the discovered and other currently known variability in space and time, leading to revised emission estimates being lower that past values. However, lakes and reservoir water surfaces still account for ca 10 % och the global methane emissions.
The project also pioneered work with low-cost sensors and automated flux chambers, hyperspectral imaging and drone-based measurements of methane and other greenhouse gas fluxes. These novel techniques at varying complexity and cost levels are very promising and will be important contributions to facilitate future greenhouse gas emissions monitoring and modelling of relevance to many more types of environments than lakes.
- There is a pronounced diel variability in lake methane emissions, typically with higher emissions daytime, that is important to be aware of when extrapolating emissions over time.
- The methane found in lakes can have different sources, including surrounding groundwater in addition to the production in the sediments.
- Phosphorous can be a key regulator of water column methane oxidation.
- With systematic sampling, covering within lake spatial variability, variability over time during all seasons as well as variability among days, and between lakes having different characteristics and in different ecoclimatic regimes, more powerful statistical models of lake methane emissions can be derived with multiple driver variables.
The global lake methane emissions were re-assessed accounting for the discovered and other currently known variability in space and time, leading to revised emission estimates being lower that past values. However, lakes and reservoir water surfaces still account for ca 10 % och the global methane emissions.
The project also pioneered work with low-cost sensors and automated flux chambers, hyperspectral imaging and drone-based measurements of methane and other greenhouse gas fluxes. These novel techniques at varying complexity and cost levels are very promising and will be important contributions to facilitate future greenhouse gas emissions monitoring and modelling of relevance to many more types of environments than lakes.
The data collection have included beyond state-of-the-art approaches, and have started to yield multi-scale and multi-system data, supplemented by experiments - together expected to provide unique information suitable for model development and validation. All information has been and will be further analysed addressing effects of scaling and environmental change and METLAKE has already shown that with systematic sampling designs based on process knowledge, flux quantification, extrapolation and prediction across scales can be much improved. The revised contemporary lake emission estimates and the novel lake emission prediction under evaluation, reached beyond project goals by being global in extent thanks to global METLAKE collaborative networks.
METLAKE has also resulted in ground-breaking progress regarding methodological development for greenhouse gas flux measurements of relevance for multiple types of flux sources/sinks in nature and industrial/urban areas. METLAKE have both improved traditional methods and contributed to development of entirely novel methodology (e.g. use of low-cost sensors, hyperspectral imaging, and drone based flux measurements.
Altogether, METLAKE has advanced our understanding of one of the largest natural methane sources, and provided systematic approaches to predict future lake emissions. Such improved quantification of feedbacks on natural greenhouse gas emissions is needed to improve global greenhouse gas budgets and enable better estimates of the mitigation efforts needed to reach global climate goals. The METLAKE expansion of the current "methods toolbox" for greenhouse gas flux measurement approaches beyond state-of-the-art, will be long-term useful in many areas of research and for society as a whole.
METLAKE has also resulted in ground-breaking progress regarding methodological development for greenhouse gas flux measurements of relevance for multiple types of flux sources/sinks in nature and industrial/urban areas. METLAKE have both improved traditional methods and contributed to development of entirely novel methodology (e.g. use of low-cost sensors, hyperspectral imaging, and drone based flux measurements.
Altogether, METLAKE has advanced our understanding of one of the largest natural methane sources, and provided systematic approaches to predict future lake emissions. Such improved quantification of feedbacks on natural greenhouse gas emissions is needed to improve global greenhouse gas budgets and enable better estimates of the mitigation efforts needed to reach global climate goals. The METLAKE expansion of the current "methods toolbox" for greenhouse gas flux measurement approaches beyond state-of-the-art, will be long-term useful in many areas of research and for society as a whole.