Collaborative Research: P2C2--El Niño Southern Oscillation (ENSO) Variability Changes during Abrupt Climate Events

The research team aims to reconstruct changes in variability of the El Nino/Southern Oscillation (ENSO) during the last deglacial period by measuring coral delta O-18 on previously collected samples from Vanuatu in the tropical southwestern Pacific Ocean. Modern coral delta O-18records from Vanuatu and pseudoproxy experiments show a high degree of skill in capturing changes in ENSO variability, providing confidence that the resulting records can be used to reconstruct past ENSO variability.

The researchers will compare the reconstructions to climate model output of ENSO during previous glacial times when Atlantic Meridional Overturning Circulation (AMOC) was both vigorous and sluggish.

The research team’s current hypotheses, based on climate model output, is that ENSO was reduced during glacial times, relative to modern, and that ENSO was more active when AMOC was shutdown, relative to contemporaneous glacial times when AMOC was active.

The team will conduct hosing model experiments under glacial boundary conditions to test the sensitivity of ENSO and AMOC changes to background conditions. The research will also investigate how non-stationarity of ENSO may affect the skills of Vanuatu corals by using an ensemble of climate models run under different climate boundary conditions.

The project may help shed light on the sensitivity of ENSO to external forcing, a highly critical issue given that climate models used for future climate projections do not agree if ENSO will strengthen or weaken as the Earth warms.

The potential Broader Impacts include a deeper understanding of ENSO variability, development of a new drilling system for field research, involvement of graduate and undergraduate students in the research including undergraduates at a primarily undergraduate teaching institution.

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.