Constraining atmosphere-terrestrial-aquatic carbon cycle processes at national and ecoregional scales with radiocarbon data: Introducing the Radiocarbon Inventories of Switzerland (RICH) project

New constraints on carbon exchanges between atmospheric, terrestrial and aquatic systems are needed to reduce uncertainty in future predictions of the global carbon cycle and climate change. Radiocarbon is a powerful tool for studying the carbon cycle due to its to its ~5700-year half-life that sheds light on processes occuring on centennial to millenial timescales, as well as the ¹⁴C “bomb spike” resulting from above-ground nuclear weapons testing in the mid-20^th Century that serves as a tracer of carbon flow among more rapidly cycling pools. The “Radiocarbon Inventories of Switzerland” (“RICH”) project is a collaborative initiative that involves undertaking a first-of-its-kind, national-scale ¹⁴C survey spanning all major carbon pools and encompassing the five different Swiss ecoregions. The project is acquiring a comprehensive “snapshot” of ¹⁴C measurements for carbon species in the atmosphere, soils and the hydrophere (e.g. ¹⁴C in atmospheric and soil-derived gas samples, ¹⁴C in bulk samples and different sub-fractions of soil, water and sediment samples), and developing historical context through ¹⁴C analysis of natural archives and of archived samples spanning the pre-bomb era to the present. The measurements are being used to study various carbon cycle processes, including turnover rates of different soil carbon fractions, budgets of riverine carbon, and anthropogenic emissions of CO₂ and CH₄. New, integrated atmospheric-terrestrial-aquatic carbon cycle models are being developed and calibrated, and existing models are being evaluated. This presentation will outline the goals and scope of the RICH project, and provide illustrations of the information that is now flowing from this collaborative undertaking. The project structure is envisioned to serve as template that can be  adapted in carbon cycle studies on regional to global scales, and the scientific outcomes will be relevant not only to Switzerland but also to the broader understanding of carbon cycle processes.