Abstract
Tropical Pacific sea surface temperature anomalies influence the atmospheric circulation, impacting climate far beyond the tropics. The predictability of the corresponding atmospheric signals is typically limited to less than 1 year lead time. Here we present observational and modelling evidence for multi-year predictability of coherent trans-basin climate variations that are characterized by a zonal seesaw in tropical sea surface temperature and sea-level pressure between the Pacific and the other two ocean basins. State-of-the-art climate model forecasts initialized from a realistic ocean state show that the low-frequency trans-basin climate variability, which explains part of the El Niño Southern Oscillation flavours, can be predicted up to 3 years ahead, thus exceeding the predictive skill of current tropical climate forecasts for natural variability. This low-frequency variability emerges from the synchronization of ocean anomalies in all basins via global reorganizations of the atmospheric Walker Circulation.
Highlights
Tropical Pacific sea surface temperature anomalies influence the atmospheric circulation, impacting climate far beyond the tropics
Our results suggest that the Atlantic Ocean plays an important role in low-frequency variability in the tropical Pacific via the atmospheric trans-basin coupling
The tropical trans-basin variability (TBV) predictability exceeds El Nino Southern Oscillation (ENSO)’s predictive skill by a factor of B3 (Fig. 4 and Supplementary Fig. 6), despite the fact that our results may be contaminated by model biases and the simple initialization technique
Summary
Tropical Pacific sea surface temperature anomalies influence the atmospheric circulation, impacting climate far beyond the tropics. State-of-the-art climate model forecasts initialized from a realistic ocean state show that the low-frequency trans-basin climate variability, which explains part of the El Nino Southern Oscillation flavours, can be predicted up to 3 years ahead, exceeding the predictive skill of current tropical climate forecasts for natural variability This low-frequency variability emerges from the synchronization of ocean anomalies in all basins via global reorganizations of the atmospheric Walker Circulation. To evaluate the impact of ocean variability in the equatorial Pacific, the Atlantic and the Indian Ocean on multi-year predictability elsewhere, we conducted a set of experiments for which observed ocean data were assimilated only in one of the ocean basins, whereas the other basins were allowed to evolve freely (see Methods) From these experiments, we show the multi-year predictive skills for the low-frequency tropical climate variability via global reorganizations of the atmospheric Walker Circulation
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