NOAA/WDS Paleoclimatology - Grand Canyon Stalagmite Stable Isotope Data during the Early Holocene

Summer rainfall is an important contributor to water budgets in western North American deserts, where intense rainfall sustains ecosystems while also causing flash floods and damaging erosion. A better understanding of Grand Canyon paleoclimate and the long-term history of the summer monsoon from summer sensitive paleoclimate records will improve our ability to project future hydroclimatic changes under warmer conditions. Here we show multi-proxy evidence for an intensification of the Early Holocene (11,700 to 8200 years ago) hydrological cycle linked to a stronger and expanded summer North American Monsoon, from calcite oxygen and uranium isotopes in a uranium-series precisely-dated stalagmite from a Grand Canyon cave. Our results suggest that subsurface infiltration was greater in the Early Holocene than today at Grand Canyon. A data-model comparison with an isotope-enabled climate model suggests that enhanced infiltration was due to an Early Holocene monsoon intensification associated with rising atmospheric temperature. Projections of a future increase in precipitation intensity or more frequent and expanded North American monsoon rain events may paradoxically result in increased subsurface infiltration at Grand Canyon and other high-altitude plateaus, even within the context of western North American aridification in a hotter climate.