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Climate change behind the highest ocean temperatures in the Pacific in 800 years


Climate change behind the highest ocean temperatures in the Pacific in 800 years

Pacific Ocean

El Niño is a periodic weather phenomenon in the tropical Pacific that has a major impact on climate, both regionally and globally. New research indicates that the ocean temperatures in the region during recent decades are the highest in 800 years.

“El Niño has a major impact on precipitation patterns in the Pacific region, such as the monsoon circulation in Asia and drought in North America, so these variations are important for much of the world’s population”, says Hans Linderholm, Professor of Physical Geography and one of the researchers behind the study.

Recently, researchers found that there are two types of El Niño. In one, anomalies in ocean temperatures are greatest in the eastern part of the tropical Pacific Ocean. The other type of El Niño has a distinct temperature anomaly pattern in the central Pacific.

These two types of El Niño have somewhat different impacts on the climate. Research shows that the latter variant has become more frequent during the last few decades, something that probably is linked with the global warming resulting from human causes.

Reconstructing past climate changes with tree rings

In a new international study, ocean temperatures in the central Pacific have been documented during the period from 1190 until 2007.

“To evaluate the central Pacific El Niño variations in in the past, we have studied isotopic data from Taiwanese tree rings”, Hans Linderholm says.

Taking samples from a tree.The researchers examined how variations in the oxygen isotopic composition in tree rings was linked with local precipitation and how rainfall amounts, in turn, were linked with water temperatures in the Pacific Ocean.

“Trees from Taiwan could thus give us information about annual variations in ocean temperatures far back in time”, says Hans.

In this way, the researchers were able to reconstruct sea-surface temperatures in the central Pacific for the past 800 years. The results show that in the last few decades, ocean temperatures in this region have been the highest during the entire studied period.

"Our conclusion is that anthropogenic climate change has had a profound effect on ocean temperatures in the central Pacific.”

Hans LinderholmHans has worked on the current study with his colleague at the University of Gothenburg, Professor Deliang Chen. The study has been led by Professor Yu Liu at the Institute of Earth Environment, Chinese Academy of Sciences, who is a visiting professor at the University of Gothenburg’s Department of Earth Sciences.

The article titled “Recent enhancement of the central Pacific El Niño variability relative to last eight centuries” appeared in the journal Nature Communications.
Link to article>>

Hans Linderholm, professor at the Department of Earth Sciences, University of Gothenburg
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Photo 1- The Pacific Ocean
Photo 2 Photo of field work, Yu Liu
Photo 3 Portrait of Hans Linderholm