Volcanic eruption signatures in the Isotope‐Enabled Last Millennium Ensemble

Explosive volcanic eruptions are one of the largest natural climate perturbations, but few observational constraints exist on either the climate responses to eruptions or the properties (size, hemispheric aerosol distribution, etc.) of the eruptions themselves. Paleoclimate records are thus important sources of information on past eruptions, often through the measurement of oxygen isotopic ratios (δ18O) in natural archives. However, since many processes affect δ18O, the dynamical interpretation of these records can be quite complex. Here we present results from new, isotope‐enabled members of the Community Earth System Model Last Millennium Ensemble, documenting eruption‐induced δ18O variations throughout the climate system. Eruptions create significant perturbations in the δ18O of precipitation and soil moisture in central/eastern North America, via excitation of the Atlantic Multidecadal Oscillation. Monsoon Asia and Australia also exhibit strong precipitation and soil δ18O anomalies; in these cases, δ18O may reflect changes to El Niño‐Southern Oscillation phase following eruptions. Salinity and seawater δ18O patterns demonstrate the importance of both local hydrologic shifts and the phasing of the El Niño‐Southern Oscillation response, both along the equator and in the subtropics. In all cases, the responses are highly sensitive to eruption latitude, which points to the utility of isotopic records in constraining aerosol distribution patterns associated with past eruptions. This is most effective using precipitation δ18O; all Southern eruptions and the majority (66%) of Northern eruptions can be correctly identified. This work thus serves as a starting point for new, quantitative uses of isotopic records for understanding volcanic impacts on climate.