CHROME · Linking Chemical diversity and Reactivity of Arctic dissolved Organic Matter for its integration in Earth system models

Organic carbon is exported from terrestrial to freshwater ecosystems where, not only is it being degraded and eventually lost as carbon dioxide, but such degradation occurs faster than in soils or marine systems. Across freshwaters, variations in organic matter degradation and reactivity have been related to compositional changes in organic matter. The flux from terrestrial to aquatic systems seems to be increasing associated to anthropogenic perturbations. However, despite the relevance of these fluxes for the global C cycle, Earth System Models (ESMs) are just starting to consider them. In that sense, a particularly crucial region deserving urgent attention is the Arctic, as permafrost soils hold a massive C stock that is vulnerable to being mobilized towards freshwaters. Such transfer could turn that vulnerable C stock from a sink into a carbon dioxide source. Therefore, determining the reactivity of that organic matter flux and incorporating it in surface models is key at the moment. The foundation of CHROME is the idea that the chemical diversity of organic matter explains its reactivity and, as such, should be considered in biogeochemical models. CHROME represents the first attempt to incorporate organic matter chemical diversity to ESMs, and will do so by: i) developing and selecting functional chemical diversity indices as indicators of Arctic organic matter reactivity and ii) implementing that knowledge in a regional branch of an ESM. CHROME is based on the good match between the previous experience of the applicant and the excellence of the host institutions, leaders in the field of biogeochemical research in Arctic ecosystems (USGS, Boulder) and in global modelling (LSCE-CNRS, France). CHROME will constitute a key advance in C biogeochemical understanding and modelling, which will position the fellow at the forefront of geosciences research.