Data from: The hydroclimate and environmental response to middle Miocene warming in the southwestern U.S.A.: Stable isotope evidence

Predictions for the southwestern US with warming often suggest increased
aridity. We investigate the sedimentary record of the Miocene Climate
Optimum and Transition (MCO and MCT; ~17-14 Ma) in northern New Mexico to
understand the impact of warmer global temperatures and higher pCO2 on
southwestern hydroclimate. The MCO and MCT comprised a globally warmer
period with elevated pCO2 similar to end-of-the-century (~400-800 ppm)
projections. We present new stable isotope (δ18O and δ13C) records of
vadose-zone and groundwater terrestrial carbonates and of modern
precipitation, stream, and groundwater from the Española basin in northern
New Mexico and establish a high-resolution age model using new 40Ar/39Ar
ages. We interpret δ18O as reflecting the balance between summertime
monsoonal and wintertime precipitation and δ13C as a reflection of plant
productivity. Terrestrial carbonate δ18O is lowest during the MCO and MCT
and is correlated with terrestrial carbonate δ13C and anti-correlated with
the benthic δ18O record. We interpret these data as recording an overall
winter-wet climate during the MCO and MCT, but that precipitation
seasonality varied in response to changes in global climate during this
period. The further correlation with carbonate δ13C suggests that plant
productivity was driven by the amount of wintertime precipitation.
Comparison with middle Miocene climate model simulations reveals that
higher CO2 drives a shift towards wintertime precipitation. Though
paleogeographic changes may obscure a direct comparison to modern warming,
overall, our findings suggest that prolonged global warmth may be
associated with increased wintertime precipitation and greater primary
productivity in northern New Mexico. These datasets contain the original
data associated with these records and in support of the
conclusions.