Spatiotemporal Methane Emission From Global Reservoirs

Abstract

AbstractInland aquatic systems, such as reservoirs, contribute substantially to global methane (CH4) emissions; yet are among the most uncertain components of the total CH4 budget. Reservoirs have received recent attention as they may generate high CH4 fluxes. Improved quantification of these CH4 fluxes, particularly their spatiotemporal distribution, is key to realistically incorporating them in CH4 modeling and budget studies. Here we report on a new global, gridded (0.25° lat × 0.25° lon) study of reservoir CH4 emissions, accounting for new knowledge regarding reservoir areal extent and distribution, and spatiotemporal emission patterns influenced by diurnal variability, temperature‐dependent seasonality, satellite‐derived freeze‐thaw dynamics, and eco‐climatic zone. The results of this new data set comprise daily CH4 emissions throughout the full annual cycle and show that reservoirs cover 297 × 103 km2 globally and emit 10.1 Tg CH4 yr−1 (1σ uncertainty range of 7.2–12.9 Tg CH4 yr−1) from diffusive (1.2 Tg CH4 yr−1) and ebullitive (8.9 Tg CH4 yr−1) emission pathways. This analysis of reservoir CH4 emission addresses multiple gaps and uncertainties in previous studies and represents an important contribution to studies of the global CH4 budget. The new data sets and methodologies from this study provide a framework to better understand and model the current and future role of reservoirs in the global CH4 budget and to guide efforts to mitigate reservoir‐related CH4 emissions.