Collaborative Research: P2C2--Hydroclimatic Response of El Nino-Southern Oscillation to Natural and Anthropogenic Radiative Forcing

This project aims to develop delta oxygen-18 isotope data series from cellulose extracted from an existing collection of ring-dated teak (Tectona grandis L. f.) tree core samples from Muna, South Sulawesi, Indonesia. Preliminary results suggest that Muna oxygen-18 is an indicator of ENSO-related precipitation variation, but with a higher signal-to-noise ratio.

Because the Muna collection contains up to 44 cross-dated increment cores, the researchers will use isotopic sampling at annual resolution with 6 replicates per year, on samples available for the years 1656-2005. This is a 350-year interval spanning both pre-industrial and anthropogenic greenhouse gas and land cover/land use change forcing levels, multiple realizations of explosive volcanic and solar forcing, and years for which net forcing is minimal.

Interpretation of the isotopic data will be tested against existing proxy sensor models using meteorological data, a new collection of precipitation oxygen-18 isotope data, and parameter sensitivity studies. Composite cellulose oxygen-18 isotope response and uncertainty estimates will be derived using estimates of the external radiative forcings estimated for the same time interval.

The researchers will test the null of no difference in inferred ENSO event return interval and amplitude using superposed epoch analysis for unforced years, volcanic event years, solar-forced decades, and pre-industrial, transitional and anthropogenic time windows for aerosol, land use/change and greenhouse gas forcings.

The potential Broader Impacts include possibly providing a new analytical technique to apply to relatively untapped and potentially critical climate archives of the tropics, support of U.S. mentored international research experiences for graduate and capstone undergraduate students at the University of Maryland, as well as support for a graduate student

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.