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Keywords:

  • decadal predictability

[1] This study quantifies the impact of ENSO on the decadal predictability of tropical Indo-Pacific Ocean trends in a very large ensemble of NCAR CCSM3 anthropogenically-forced (A1B scenario) simulations, by decomposing upper ocean temperatures into “ENSO” and “non-ENSO” variability. On decadal time scales, the ENSO pattern primarily contributes to the ensemble spread and has a trend whose amplitude is not predictable. However, the non-ENSO component of the trend has much smaller spread and is predictable after 10 years, much sooner than the total trend, which is predictable after 25 years. The non-ENSO component of the trend explains 96% of the total trend and has a structure that is distinct from ENSO, including cooling in the South Pacific due to increased southeast trades, warming of the warm pool, and strengthening of the equatorial Pacific near-surface temperature gradient superimposed upon a uniform warming.