PP41D-06
Identifying Oxygen Isotopic Signatures of ENSO Dynamics Through Isotope-Enabled Regional Ocean Modeling

Thursday, 17 December 2015: 09:15
2010 (Moscone West)
Samantha Stevenson, National Center for Atmospheric Research, Boulder, CO, United States; University of Hawaii, Honolulu, HI, United States, Brian Powell, University of Hawaii at Manoa, Honolulu, HI, United States, Mark A Merrifield, Sch Ocean & Earth Sci & Tech, Honolulu, HI, United States, Kim M Cobb, Georgia Institute of Technology Main Campus, Earth and Atmospheric Sciences, Atlanta, GA, United States, Jesse M Nusbaumer, University of Colorado at Boulder, Atmospheric and Oceanic Sciences, Boulder, CO, United States and David C Noone, Dept Atmospheric & Oceanic Sci, Boulder, CO, United States
Abstract:
Coral oxygen isotope (δ18O) records provide important constraints on past variability in the El Nino/Southern Oscillation (ENSO). However, the relationship between ENSO activity and δ18O anomalies is subject to a high degree of uncertainty owing to both observational limitations and poorly understood dynamical processes. The isotope-enabled Regional Ocean Modeling System (isoROMS) is designed to address some of these uncertainties; isoROMS is a flexible modeling framework capable of simulating δ18O over an arbitrary domain at a variety of spatial resolutions. Initial results for isoROMS simulations at the central equatorial Pacific Line Islands chain over the 1979-2009 period are presented, using water isotopologue fluxes taken from the isotope-enabled NCAR Community Atmosphere Model (iCAM). Mesoscale ocean processes can significantly impact temperature and seawater δ18O variability under certain conditions, particularly during strong La Nina events. The variability in the ENSO/δ18O relationship is then investigated over the 20th century using a suite of isoROMS simulations conducted with combinations of atmosphere and ocean reanalysis products, in an effort to determine the optimal form of 'forward models' for predicting δ18O given local conditions. Implications for our ability to quantitatively reconstruct ENSO amplitude and the properties of El Nino/La Nina events are discussed.