Frerk Poeppelmeier
Frerk Pöppelmeier is an Assistant Professor in Global Biogeochemical Modelling at the University of Bern, Switzerland, working on the reconstruction of ocean circulation and climate change during the Quaternary. With a background in isotope geochemistry and paleoceanography, he has transitioned to Earth system modelling, where he integrates direct reconstructions from marine sediments with model simulations. Frerk’s research interests cover a broad range of topics, including the geochemical understanding of trace elements in the ocean and sediments used to reconstruct water mass properties, the stability conditions of the AMOC and it’s influence on the carbon cycle, and the interaction of continental ice sheets with the ocean during glacial-interglacial cycles.
Constraining past ocean circulation with proxy-enabled Earth system models
The ocean circulation is a key Earth system component, both driving and responding to climate change on centennial to millennial timescales. Future ocean carbon and heat uptake will therefore play a critical role in shaping the climate state by the end of this century and beyond. However, Earth system models face persistent challenges in accurately representing deep ocean circulation and carbon storage, due to limited observational constraints and an incomplete understanding of underlying dynamics. By employing proxy-enabled Earth system models to simulate past abrupt climate transitions, we can derive robust constraints on the ocean’s role in climate variability on centennial to millennial timescales. The direct implementation of these tracers not only strengthens our mechanistic understanding of proxies, but also allows to include their uncertainties in the model-derived ocean state estimates. Here, we demonstrate this approach using the Bern3D Earth system model of intermediate complexity, which includes explicit representations of carbon, neodymium, beryllium, protactinium, and thorium isotopes as well as additional trace elements, such as noble gases, N2O, and chromium. By employing multiple proxies in this coherent framework, we constrain past Atlantic overturning circulation for the last deglaciation and Dansgaard-Oeschger Events. In contrast to previous findings, our direct model-data comparison indicates that the Atlantic circulation never came to a complete halt, even during the freshwater perturbations associated with Heinrich Events. The complex interactions of biogeochemical and physical processes affecting proxy records underscore the need for more careful considerations when interpreting paleo-reconstructions.
