Department Seminar: Margot White

Title: Radiocarbon-based insights into the role of aquatic systems in the global carbon cycle

Abstract: Delineating how climate change impacts natural carbon cycles requires a thorough understanding of reservoirs, fluxes, and processes - a task for which natural abundance radiocarbon is uniquely suited. In the first part of this talk, I will discuss efforts to establish a first of its kind national inventory of radiocarbon for the country of Switzerland, with an emphasis on the role of aquatic systems as transporters, integrators, and processors of carbon. This project will generate a framework that can be applied across different terrestrial systems to examine the response of the carbon cycle to climate change and other anthropogenic pressures. The second part of the talk will focus on the marine dissolved organic carbon (DOC) reservoir- a large store of carbon whose interactions with the global carbon cycle remain largely unconstrained. The average radiocarbon signature of this reservoir suggests that some components are unreactive (refractory) and spend an average of >5000 radiocarbon years in the ocean, but the distribution of radiocarbon ages within marine DOC is not known. I will discuss the application of chemical and thermal degradation techniques to operationally isolate refractory DOC (RDOC). While RDOC shares chemical characteristics in the surface and deep ocean, an observed radiocarbon gradient with depth challenges established notions about the source and residence time of RDOC in the marine water column. Future work will harness advances in radiocarbon measurement combined with novel techniques for the chemical characterization of natural organic matter to further constrain the rate of exchange of carbon between reservoirs of the active global carbon cycle