« Rivers flow not past, but through »: a fluvial perspective on the global cycling of carbon, sulfur, and alkalinity

The amounts of carbon dioxide (CO?) and oxygen (O?) in Earth's atmosphere are controlled, in part, by chemical reactions occuring at Earth's surface. In order to understand and predict past and future changes in CO? and O?, we must determine how the relevant reactions vary in space and time. River systems in particular have provided crucial insights into the global controls on near-surface chemical reaction as they record the relevant processes integrated over their catchment area. Here, I report ongoing work on river systems aimed at determining the role of climate in controlling chemical reaction using seasonal and glacial-interglacial cycles as case studies. For this work, we explicity consider the hydrologic (water transit times) and geomorphic (incision and meandering) proceses that influence rivers and their roles in controlling reaction progress. Further, we utilize various isotopic systems including hydrogen, sulfur, and radiocarbon to constrain reaction timescales and identify solute sources.