Southwest Pacific Ocean Circulation and Climate Experiment (SPICE) - Part I. Scientific Background

South Pacific thermocline waters are transported in the westward flowing South Equatorial Current from the subtropical gyre center toward the southwestern Pacific Ocean—a major circulation pathway that redistributes water from the subtropics to the equator and to the southern ocean. The transit in the Coral Sea is potentially of great importance to tropical climate prediction because changes in either the temperature or the amount of water arriving at the equator have the capability to modulate the El Niño-Southern Oscillation (ENSO; glossary of acronyms at the end of the document) cycle and thereby produce basin-scale climate feedbacks. The southern fate of thermocline waters is, comparably, of major influence on Australia and New Zealand’s climate; its seasonal and interannual evolution influences air-sea heat flux and atmospheric conditions, and it participates in the combined south Indian and Pacific Ocean “supergyre.” Substantial changes of this circulation have been observed over the past 50 years, and are continuing in global climate projections. The subtropical gyre has been spinning up in recent years with possible consequences for ENSO modulation and for the East Australian Current (EAC), whose influence has moved south, dramatically affecting the climate and biodiversity of Tasmania.