Department Seminar: Marisa Repasch
Title: The role of rivers in the global carbon cycle: linking geomorphic and geochemical processes
Abstract: The global carbon cycle describes the circulation of carbon through our planet’s major reservoirs, primarily the biosphere (living plants), the oceans, the lithosphere (rocks), and the atmosphere. The amount of carbon in our atmosphere regulates Earth’s surface temperature, and ultimately the ability of our planet to sustain life. To understand how the amount of carbon stored in these reservoirs changes through time, we need to develop a mechanistic understanding of the processes (both natural and anthropogenic) that drive carbon fluxes into and out of each reservoir. In this talk, I focus on the role of rivers in the organic carbon (OC) cycle. OC is produced by plants and is transferred to soil when plants die or lose their leaves seasonally. Soil can be eroded into rivers, which transfer OC from the biosphere into the oceans. Because OC molecules are not stable at Earth’s surface, they can be transformed into carbon dioxide during downstream transit in rivers, resulting in a flux of carbon dioxide to the atmosphere. The fate of OC in rivers can vary depending on channel-floodplain dynamics and regional climate. I combine organic and inorganic geochemistry to study the dynamics of river sediment transport and how these dynamics influence the fluxes of carbon in rivers over annual to millennial timescales. These data can help propel the advancement of Earth system models that need constraints on the linkages between physical and geochemical processes at Earth’s surface.