Projected Shifts of the South Pacific Convergence Zone and Their Effect on ENSO and Sea Level Extremes

Monday, 15 December 2014
Axel Timmermann1, Matthew J Widlansky2, Shayne McGregor3, Malte F Stuecker2 and Wenju Cai4, (1)IPRC-SOEST, Honolulu, HI, United States, (2)University of Hawaii at Manoa, Honolulu, HI, United States, (3)University of New South Wales, Sydney, Australia, (4)CSIRO, Aspendale, Australia
The South Pacific Convergence Zone (SPCZ), one of the largest rainbands on our planet, swings back and forth on annual, interannual, decadal and millennial timescales. During strong El Nino events the SPCZ collapses onto the equator which enhances drought conditions for many South Pacific Islands. Resulting wind stress curl changes in turn cause massive sea-level drops of about to 30 cm ('Taimasa' events - Samoan for smelly reef), which further impact Island communities. These so-called zonal SPCZ events emerge through the nonlinear interaction between ENSO and the annual cycle (combination mode). Their effect on zonal equatorial winds has been identified as one of the key terminators for strong El Nino events and as an important seasonal modulator for ENSO. Recent modeling studies have demonstrated that the number of zonal SPCZ events may nearly double in response to greenhouse warming over the next century. This presentation will discuss the impacts of future projected SPCZ changes on the characteristics of El Nino and on regional sea-level extremes in the South Pacific.