RSI Research Seminar

Join us every other Monday at noon for lunch and a 30-minute research talk, presented by Resnick Sustainability Institute Graduate Fellows and Caltech researchers funded by the Resnick Sustainability Institute. To see the full schedule of speakers, visit the RSI Research Seminar web page. Seminars currently take place in a hybrid format, both in-person (Jorgensen building first-floor conference room) and via Zoom. For more information and to get the Zoom login info, please reach out to [email protected]

Quantifying carbon stock and cycling in the Yukon River basin

Arctic warming is causing permafrost thaw, which is destabilizing riverbanks and accelerating erosion. Meanwhile, bank erosion liberates frozen soils, which contain abundant organic carbon (OC). Arctic permafrost contains approximately 1300 × 10³ Mt of OC, a substantial fraction is active compounds preserved for hundreds to thousands of years. This amount accounts for around 50% of global soil OC in only 15% of land area and more than two times the size of the global pre-industrial atmospheric carbon (590 × 10³ Mt) (Schuur et al., 2015; Jorgenson et al., 2013; Hugelius et al., 2014). Eroded solids are transported in the form of suspended particulate matter (SPM) in the fluvial system, carrying terrestrial OC in the form of particulate organic carbon (POC), redistributing eroded OC to varying geomorphic units. This carbon can be explained by a dominant fraction of OC derived from the terrestrial biosphere (OC_bio) and a minor fraction eroded from sedimentary rocks (OC_petro). Giant amount of OC_bio can be liberated by bank erosion, leading to different fates, i.e.., respired as CO₂, converted to methane (CH₄), or redeposited and preserved in sediments. Oxidative degradation of OC_bio and produces CO₂ back to the atmosphere over the present to millennial timescales depending on the residence time of OC_bio, while if OC_petro is oxidized along its fluvial (e.g., floodplains) and marine pathway or directly in rocks at the continental surface (e.g., in shales), it could act as positive feedback to the atmospheric CO₂ over geologic timescales. Both processes act as positive feedback on global climate and can be potentially enhanced If riverbank erosion rates increase in warming climate, in which erosion driven by warming releases greenhouse gases that in turn accelerate warming. The large amounts of OC stored in permafrost underline the potential importance of these processes for the global climate system, yet we lack basic knowledge of river erosion, its response to warming, and its impact on carbon fluxes from permafrost.