Professor Ellen Thomas of Yale University presents the second lecture of the Tsaihwa “James” Chow lecture series, ‘Geological Record of Effects of Global Warming on Oceanic Export and Primary Productivity.’ Deep-sea organisms dominantly depend upon organic matter produced in the surface waters of the oceans, and the efficiency of its transfer to their seafloor habitat. The accumulation rate of benthic foraminifera (BFAR) has been used as a proxy for primary productivity, but reflects the amount of food arriving on the seafloor, thus some combination of Net Primary Productivity (NPP) and the efficiency of the biological pump. NPP is not necessarily the primary control on export flux, because ecosystem structure is important in affecting recycling in upper waters. Biogenic Barium accumulation rates (BioBaAR) have, like BFAR, been used as a proxy for NPP, but barite forms in the oceanic water column at mid water depths, in microenvironments where sinking organic matter is decomposed. Accordingly, higher BioBaARs indicate that more organic C was transported out of the euphotic zone and into deeper waters, where it was regenerated enhancing barite formation and accumulation, and thus not transported to the sea floor. We compare BFAR and BioBaAR across Eocene hyperthermal events, in order to evaluate changes in productivity and organic matter remineralization across past episodes of global warming, and effects of increased metabolic rates and changing oceanic ecosystems on carbon sequestration in the deep sea. Learn more about Dr. Thomas: https://people.earth.yale.edu/profile/ellen-thomas/about The lecture series is named for Dr. Tsaihwa J. Chow, a geochemist with a long association with Scripps who died in 2006. Snacks will be served following the seminar.