Super El Nino could well have had an Indian Ocean trigger, say Japanese researchers

The super 'El Ninos' (the likes of 1972, 1982 and 1997) with devastating impacts worldwide could well have been the handiwork of a villain traced to no farther away than in the Indian Ocean.

A study by a team led by Saji N Hameed, Professor at University of Aizu, Japan, has shown for the first time that the Indian Ocean Dipole (IOD) events are a key factor in the generation of super El Ninos.

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Noting that the years of super El Ninos co-occurred with IOD events (a phenomenon similar to El Nino, but generated by processes inherent to the Indian Ocean), the researchers explored possible mechanisms linking both phenomena.

They found that while Pacific processes are needed to initiate El Ninos, it was the extra energy generated by the IOD, and transferred to the Pacific through atmospheric pathways, which eventually transformed the El Nino into a super El Nino event.

The study, titled 'A model for super El Ninos' has been published in Nature Communications , Saji Hameed wrote in an e-mail to BusinessLine . In this manner, the University of Aizu team has identified two distinct Indo-Pacific processes shaping the unique features and extraordinary ferocity of super El Ninos.

Elusive super El Ninos

A systematic analysis of these processes and their interactions will improve the forecasts for elusive super El Ninos, the researchers claim.

One of the most powerful El Ninos in 1972 set off economic shock waves when it utterly devastated the Peruvian anchovy fishing industry and drove global food production per capita and global food reserves to their lowest level since the end of World War II.

With the arrival of the powerful El Ninos of 1982 and 1997, scientists felt the need for a new term ‘'super El Nino' to describe these extraordinarily strong El Nino events.

"Till recently, scientists believed that climate and weather processes operating within the Pacific Ocean could explain the occurrence of super El Ninos. The infamously failed prediction of the 2014 super El Nino event had its root in these assumptions," says Saji Hameed.

Computational simulation

To unveil the mechanisms of super El Ninos, Hameed and his colleagues conducted computational simulations that recreated selected Pacific Ocean processes involved in the generation of El Ninos. To their surprise, they discovered a new mechanism embedded within the Pacific Ocean, which prevented sea surface temperatures (SSTs) in the far-eastern Pacific rising too far above normal.

"Extremely warm sea surface temperatures are a notable feature of the super El Ninos," said Dachao Jin, co-author of the study, who was a visiting scientist from the Nanjing University of Information Science and Technology at that time.

"The fact that Pacific Ocean processes responsible for generating regular El Ninos could not explain this key signature of super El Ninos came as a big shock", he added.

Meanwhile, responding to a specific question, Hameed told BusinessLine that he was not very sure “'if what we are going to see concurrently in the Pacific’’ is an El Nino.

"There has been strong decadal SST variations since 2012, and my feeling is that we are still seeing some remnants of that. The situation with IOD is also not yet clear as on date."

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