Collaborative Research: Characterizing the drivers of hydroclimate change over western North America and Europe in response to the global warmth of the middle Miocene

A key question facing society is how will water availability change as the Earth’s climate system responds to the accumulation of greenhouse gases. To address this question, a team of researchers are investigating the environmental conditions during the mid-Miocene, an interval around 15 million years ago, when the planet was in a warm climate state. The western US and Europe have experienced drying in recent decades, a trend that has been forecast to intensify as our planet warms. However, recent reconstructions of Miocene climate suggest wetter rather than drier conditions associated with past warm intervals. This project aims to understand and model rainfall during warm climate intervals in the Miocene to determine how water availability may change with warming temperatures. The collaborative project supports early career and mid-career scientists who provide graduate and high school traineeships for climate modeling at George Mason University and graduate and undergraduate traineeships in climate reconstruction at the University of Southern California. Research findings are being shared with the public through community lectures at nature centers in Virginia and Pennsylvania as well as via a partnership with University of Southern California’s communication school and the Natural History Museum of Los Angeles County’s Miocene climate exhibit. The research aims to resolve the persistent hydroclimate uncertainty in a warming climate with a model-data integration approach. Low-resolution climate simulations test hydroclimate response to ocean temperature reconstructions and sensitivity to proxy uncertainty and coverage. High-resolution simulations better resolve the North American Monsoon and atmospheric rivers, which critically determine extreme precipitation events and the subsequent wetter climate state than the current and projected drying trends. Aiming to fill data gaps for understanding western US hydroclimate, the project generates additional proxy reconstructions of ocean temperature and terrestrial hydroclimate. Extracted hydroclimate evidence from geological, botanical, and faunal records are processed into a usable data framework for comparison to climate models and the general scientific community. This model-proxy approach illuminates processes, sensitivities, and tipping points in our climate future, including a possible shift from a drier to wetter environment with warming. 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.