Are El Niño events becoming more common? Coral reef study tracing 400 years of seasonal changes reveals ‘unprecedented’ activity in the last three decades
- Like tree rings, coral cores hold growth patterns, isotopes spanning their history
- Researchers pieced together 400 years of El Nino activity using coral cores
- They found events appear to be more frequent in central Pacific in last 30 years
Scientists have extracted a 400-year record of El Niño events using coral reef cores drilled from the Pacific Ocean, revealing crucial new insight on how these weather patterns have changed.
And, the data so far suggest something ‘unusual’ has been happening in recent decades.
According to the new research, El Niño events appear to be cropping up more frequently in the central Pacific than they have in past centuries, and while eastern El Niños may be getting stronger.
Scroll down for video
Scientists have extracted a 400-year record of El Niño events using coral reef cores drilled from the Pacific Ocean, revealing crucial new insight on how these weather patterns have changed
WHAT IS EL NINO?
El Niño is caused by a shift in the distribution of warm water in the Pacific Ocean around the equator.
Usually the wind blows strongly from east to west, due to the rotation of the Earth, causing water to pile up in the western part of the Pacific.
This pulls up colder water from the deep ocean in the eastern Pacific.
However, in an El Niño, the winds pushing the water get weaker and cause the warmer water to shift back towards the east. This causes the eastern Pacific to get warmer.
But as the ocean temperature is linked to the wind currents, this causes the winds to grow weaker still and so the ocean grows warmer, meaning the El Niño grows.
This change in air and ocean currents around the equator can have a major impact on the weather patterns around the globe by creating pressure anomalies in the atmosphere.
A team of scientists from the University of New South Wales developed a method to obtain the centuries-long seasonal record using coral cores – a feat previously thought to be impossible.
Much like tree rings, coral cores hold growth patterns and isotopes that can provide information about the local environmental history.
By combining this with machine learning techniques, the team was able to piece together the record going back 400 years and compare this with the more recent data.
‘We are seeing more El Niños forming in the central Pacific Ocean in recent decades, which is unusual across the past 400 years,’ said lead author Dr Mandy Freund.
‘There are even some early hints that the much stronger Eastern Pacific El Niños, like those that occurred in 1997/98 and 2015/16 may be growing in intensity.’
According to the researchers, the El Niño events in the last 30 years included the strongest ever recorded between both the 100-year instrumental record and the historical record obtained from the coral.
‘By understanding the past, we are better equipped to understand the future, especially in the context of climate change,’ said Dr Freund.
‘Prior to this research, we did not know how frequently different types of El Niño occurred in past centuries,’ said co-author from the Centre of Excellence for Climate Extremes Dr Ben Henley. ‘Now we do.’
The researchers say the El Niño behavior observed in the central Pacific over the last few decades is unprecedented compared to past centuries.
This new insight could now help scientists prepare for future events.
‘The El Nino phenomenon is one of the most important features of global climate, and changes to its behavior have very serious implications for weather patterns and extreme events around the world,’ Dr Henley said.
‘This gives us an opportunity to more accurately explore how global warming may change El Niños and what this means for future weather and climate extremes.
‘Having a better understanding of how different types of El Niños have affected us in the past and present, will mean we are more able to model, predict, and plan for future El Niños and their wide-ranging impacts.’