Impact of Multidecadal Fluctuations in the Atlantic Thermohaline Circulation on Indo-Pacific Climate Variability in a Coupled GCM

Abstract

Using a multicentury integration of the third climate configuration of the Met Office Unified Model (HadCM3), the authors show that naturally occurring fluctuations in the Atlantic?s thermohaline circulation (THC) drive small but statistically significant changes in surface air temperature, sea level pressure, and precipitation over the Indo-Pacific region. The surface temperature component of these variations may be described as an interhemispheric seesaw (consistent with earlier studies), with changes in the Southern Hemisphere smaller than those in the Northern Hemisphere. Links between THC variability and variability related to the interdecadal Pacific oscillation (IPO) are evident: when the THC is strong (weak) the IPO variance decreases (increases) considerably, and cold (La Niña?like) IPO events tend to be stronger and more frequent when the THC is in a weak phase. This highlights the possibility that a small part of Indo-Pacific climate variability at multidecadal time scales, including some of the variability linked to the IPO, may be predictable.