Eastern Pacific El Niño activated by the Atlantic Ocean

Understanding of different types of El Niño events, notably Eastern Pacific (EP) and Central Pacific (CP) El Niño, is hindered by the limited length of observations. Using climate simulations, we investigated the evolution of El Niño flavor from 250 million years ago (Ma) to present. Results show that El Niño has been persistent throughout the entire period the simulation spans, but was dominated by CP El Niño at 250 Ma - 80 Ma. With the emergence of the Atlantic Ocean, which modulated the state of the Pacific Ocean through atmospheric circulation, EP El Niño became the predominant El Nino state (70 Ma - 10 Ma). After the closure of the Central American Seaway (0 Ma), EP and CP El Niño occurred with similar frequencies. Our findings highlight that El Niño types are controlled by geography over tectonic timescales.