Neogene hydroclimate in the US Southwest

Global climate models increasingly project that the US Southwest will get substantially drier as atmospheric CO2 rises. Wintertime precipitation will likely decrease and, combined with rising temperatures that increase evaporation, this will lead to a large decrease in river flow. However, the geologic record in the Southwest during past warm periods (such as the mid-Pliocene Warm Period) do not unequivocally show drying; instead, the Pliocene Southwest seems to have had widespread lakes and denser vegetation. We are working to reconcile these geologic observations with model projections and to understand whether the models are missing critical, long-term processes that might, actually, lead to a wetter Southwest under high atmospheric CO2 or whether are interpretations of the geologic evidence is incorrect. To do so, we are taking advantage of the remarkable terrestrial sedimentary record of Neogene climate preserved in the Santa Fe Group within the northern and central Rio Grande Rift in New Mexico.