On May 29th, Professor Derek Vance from the Swiss Federal Institute of Technology in Zurich visited SESS and delivered an academic talk titled "A bottom-up versus a top-down view of ocean biogeochemistry" .
The oceanic biogeochemical cycles of trace metals (and their isotope systems) are often thought of as being dominated by “top-down” processes. This talk presents data that support a very different, “bottom-up”, view. While top-down transfer metals from the surface to the deep by biological uptake and regeneration is an important process, recent GEOTRACES data suggest that biological particulates are not important scavengers of trace metals. These data instead suggest that Mn oxides are the dominant scavengers. Such oxides are not re-dissolved in the oxic deep ocean, Instead, high deep ocean concentrations are maintained by fluxes across the sediment-water interface, driven by the supply of metals to pore waters by diagenetic reactions. This new framework has important implications both for modern controls on ocean biogeochemistry and the interpretation of sedimentary records of the past ocean.
Derek Vance is a Full Professor at the Department of Earth Sciences of ETH Zürich. He is a geochemist whose research has addressed a wide range of fundamental questions in the earth sciences through his development and application of novel geochemical methodologies. He has quantified the timescales on which mountain ranges are uplifted and eroded. His analytical and conceptual advances have constrained the rates and long-term variability of chemical weathering. He has used new isotope measurements of transition metals to understand biogeochemical cycles in the ocean. His discoveries range across time, from establishing markers for early life, through the chemical consequences of glacial cycles, to the chemical processes critical to the present and future surface-earth environment. After spending 25 years in UK universities, he became Professor of Geochemistry at the Department of Earth Sciences, ETH Zürich, in 2012. He has acted as department head (2019-2022) and has served as President of the European Association of Geochemistry. In 2023, Derek was elected Fellow of the Royal Society.
