Carbon fluxes in Arctic and sub-Arctic freshwater ecosystems

Arctic and sub-Arctic regions host a large number of waterbodies that serve as carbon sources to the atmosphere within an environment that is predominantly characterized by carbon sequestration. The ongoing permafrost thaw in the warming Arctic is anticipated to alter the distribution of freshwater ecosystems, subsequently affecting their contribution to the overall carbon budget. Estimates of global carbon budgets largely disregard emissions caused by permafrost thaw, and also carbon budgets for freshwater ecosystems are highly uncertain to date. A general constraint in this field is data scarcity from remote northern regions. In addition, underlying processes specific to freshwater ecosystems remain poorly understood, especially given the landscape heterogeneity in high northern latitudes. To fill these gaps, our project aims at synthesizing new and existing carbon dioxide (CO2) and methane (CH4) flux data from freshwater ecosystems accompanied by environmental parameters (temperature, pH, water depth, etc.) across the Arctic-boreal domain on a site-level and at monthly resolution. This work is conceptually based on a range of previously published studies and will contribute to the Arctic-boreal carbon flux synthesis (ABCflux v2) that spans terrestrial, wetland and freshwater ecosystems. As of January 2024, we gathered data from almost 900 different freshwater sites with more than 2000 monthly CO2 and CH4 flux measurements. With the newly synthesized data, we aim to quantify the carbon budgets of freshwater ecosystems across the Arctic-boreal domain and evaluate their contribution to the global carbon budget. Additionally, the impact of environmental controls including temperature, pH, and water depth on the carbon cycle processes will be investigated. This dataset will provide a unique opportunity for benchmarking and verification of process-based models and remote sensing products. Finally, the synthesized dataset will be publicly available to the scientific community.