Collaborative Research: Quantitative Paleoclimatology of the East African Monsoon

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). The East African Monsoon (EAM) provides intense, seasonal rains that are critically linked to food security and infrastructure for a large portion of global population. The timing and amount of these rains are projected to change substantially under anthropogenic climate change. Studying past intervals of global warmth can inform the scientific community and general public on the direction and magnitude of change in EAM characteristics as the planet warms and cools. This project aims to leverage a large archive of fossil soil (paleosol) samples collected from the Baringo Basin of Kenya, Africa, to reconstruct aspects of past hydroclimate and temperature during the Pliocene-Pleistocene epochs (~4.1-2.6 million years ago). This work will produce the first quantitative estimates of precipitation and temperature across intervals of warming and cooling, including the last time that atmospheric CO2 reached current levels. The response of vegetation to these climate changes will be also be documented, thereby informing the scientific community on the sensitivity of different plant groups to changes in climate parameters. This work will support a large cohort of undergraduate student researchers and a PhD student, and scientific results will be incorporated into upper level, data-driven geoscience courses. Paleosols were previously described in the field in the vicinity of a coring locality associated with the Hominin Sites and Paleolakes Drilling Project. New analyses will include reconstructing paleoclimate (rainfall, temperature) using robust, multivariate models based on paleosol bulk geochemistry as well as the clumped isotope composition of pedogenic carbonates; vegetation will be reconstructed using stable isotopes from pedogenic carbonates and organic matter. This work will provide the first quantitative paleoclimate estimates from the Baringo Basin, which contains the most continuous Neogene stratigraphic record in equatorial eastern Africa and preserves a rich paleontological and paleoanthropological archive. The results of this work will be placed within an existing, high-resolution geochronologic framework to test hypotheses that relate the effect of CO2 rise to EAM strength, local climate seasonality, and landscape-scale vegetation structure. The project will include outcrop-to-core comparisons to evaluate proxy robustness, thereby strengthening paleoclimate and paleoenvironmental interpretations. The multi-proxy approach will allow for rigorous testing of proxy robustness and repeatability. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.