Insights into contrasting ENSO influence on SST variations off Australia’s southeast and west coasts

Abstract

El Niño–Southern Oscillation (ENSO) affects sea surface temperatures (SSTs) around the world with varying degrees of influence. Dynamical understanding of global SST responses to ENSO has progressed substantially, but is far from complete. We propose a novel modelling approach, and use it to investigate why SSTs along Australia’s southeast coast are modulated by ENSO much less strongly than along Australia’s west coast. Combining tropical Pacific pacemaker ensemble simulations and ocean model perturbation experiments, this modelling approach identifies and compares the contributions of different mechanisms for the two regions. Off Australia’s west coast, the strong ENSO signature in SST variability is dominated by remote tropical Pacific ENSO-driven wind stress forcing via oceanic teleconnections, with smaller contributions from non-ENSO climate variability. However, off the southeast coast, the contribution from remote tropical Pacific ENSO-driven wind stress forcing is largely offset by the thermodynamic ENSO-driven buoyancy forcing locally within the Coral and Tasman Sea. This resultant weak ENSO signature in SST is further weakened by non-ENSO climate variability.