Tropical climate variability: interactions across the Pacific, Indian, and Atlantic Oceans

Complex interactions manifest between modesof tropical climate variability across the Pacific, Indian, andAtlantic Oceans. For example, the El Niño–Southern Oscillation(ENSO) extends its influence on modes of variabilityin the tropical Indian and Atlantic Oceans, which in turnfeed back onto ENSO. Interactions between pairs of modescan alter their strength, periodicity, seasonality, and ultimatelytheir predictability, yet little is known about the rolethat a third mode plays. Here we examine the interactionsand relative influences between pairs of climate modesusing ensembles of 100-year partially coupled experimentsin an otherwise fully coupled general circulation model. Inthese experiments, the air–sea interaction over each tropicalocean basin, as well as pairs of ocean basins, is suppressedin turn. We find that Indian Ocean variability has a netdamping effect on ENSO and Atlantic Ocean variability,and conversely they each promote Indian Ocean variability.The connection between the Pacific and the Atlantic is mostclearly revealed in the absence of Indian Ocean variability.Our model runs suggest a weak damping influence byAtlantic variability on ENSO, and an enhancing influenceby ENSO on Atlantic variability