Jacob Slawson

and 2 more

The Earth is transitioning to a state unprecedented in human history. This transition poses a challenge for predicting the future, as climate models require testing and calibration with real-world data from high greenhouse gas climates. Despite significant progress in climate modeling, changes in the precipitation remain highly uncertain. The Paleocene-Eocene Thermal Maximum (PETM) was the warmest period of the Cenozoic Era, and thus serves as a test-bed of how precipitation is altered by extreme greenhouse gas warming. Here, we use paleosol bulk geochemistry methods to quantify changes in precipitation during the PETM in the Uinta Basin, Utah. We find no change in mean annual precipitation during this warming event. However, paleosol mass balance results track increased translocation of carbonates, increased clay illuviation, and increased accumulation of redox-sensitive elements. These results, along with shifts in fluvial stratigraphy provide evidence for increased intensity and intermittency of extreme precipitation events that may be related to changes in the transport direction, seasonality, and moisture transport capability of the North American monsoon. Surprisingly, changes in fluvial stratigraphy continued for 105-106 years after the PETM while paleosol geochemistry returned to pre-PETM conditions almost immediately at the boundary, suggesting persistent changes in precipitation intensity despite a decrease in global temperature. These findings provide further support for an intensification of the hydrological cycle during and after the PETM, provide evidence for a decoupling between mean and extreme precipitation, and indicate the importance of multi-proxy, regional studies for understanding the complexities of climate change.