Contrasting Isotopic Signatures of Recent Extreme El Nino Events

Samantha Stevenson, University of California Santa Barbara, Bren School of Environmental Science & Management, Santa Barbara, CA, United States, Brian Powell, Univ. of Hawaii, Honolulu, HI, United States, Kim M Cobb, Georgia Institute of Technology Main Campus, Department of Earth and Atmospheric Sciences, Atlanta, GA, United States, Mark Merrifield, University of California San Diego, Integrative Oceanography Division, La Jolla, CA, United States and Gemma O'Connor, Georgia Institute of Technology Main Campus, Earth and Atmospheric Sciences, Atlanta, GA, United States
Abstract:
The El Nino/Southern Oscillation (ENSO) drives the majority of interannual climate variability, and is expected to be strongly influenced by anthropogenic climate change. However, the long timescales of internal ENSO modulation require that paleoclimate information be used in order to create a sufficiently long observational baseline to ensure robust ENSO statistics. Previous work using coral oxygen isotopic records (δ18O) indicates that ENSO variability may be increasing, but the role of external forcing remains unclear - as do potential contributions from changes to hydrological influences on δ18O. Here we present results from the isotope-enabled Regional Ocean Modeling System (isoROMS), combined with physical oceanographic and water oxygen isotopic information collected from the central equatorial Pacific during the 2015-16 extreme El Nino. isoROMS provides a spatially and temporally complete dataset, which can be used to understand dynamical differences between the 2015-16 El Nino and other extreme El Nino events during the observational period. This allows us to construct δ18O-based metrics associated with extreme El Nino events, and to quantify the mechanisms for differences among δ18O signatures. This work has significant implications for reconstructing past changes to ENSO dynamics and the associated hydrological impacts.