Study reveals the vast patch of warm water has produced a dry ridge of high pressure across the south Pacific, blocking storms from reaching Chile
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Scientists believe the hot blob off the east coast of New
Zealand is contributing to a decade long drought in Chile.
Photograph: National Oceanic and Atmospheric Administration
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Researchers based in New Zealand and Chile have examined the rapidly warming hot blob which rose to prominence in 2019 after spikes in water temperature of up to 6C were recorded.
In the new study, published in the Journal of Climate, the scientists used computer simulations to investigate whether there was a link between the blob, which spans an area about the size of Australia, and years of low winter rainfall in Chile.
Their models found the blob produced a dry ridge of high pressure across the south Pacific that blocked storms from reaching central Chile and pushed them towards west Antarctica.
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“When we took the blob out of our simulations that ridge of high pressure disappears.
“That was one our biggest pieces of evidence that the blob is a major contributor [to the drought].”
The ongoing drought has reduced fresh water supplies in Chile and prompted the science minister, Andres Couve, to say this month the decline of water reserves due to climate change was a national priority.
Clem said the researchers ran models that examined a 40 year period from 1979 through to 2018.
He said the simulations found that natural variability and reduced rainfall in the tropical central Pacific allowed a blob to form, even without the influence of human-caused global heating.
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They found the blob had warmed 1.5C over the 40 year period, about three times the global average increase in sea surface temperature.
“The remarkable rate of warming in the blob contributes to a stronger ridge of high pressure across the southern Pacific,” Clem said.
“So what’s worrying – and this is the next area of research that we’re going to go down – is we need to understand the physical mechanisms that are maintaining the blob for such a long period of time.”
James Renwick is the head of geography, environment and earth sciences at Victoria University in Wellington. He was not an author on the paper but has studied the blob in the past.
He said the patch of warm ocean had been present for a long time but had not been the subject of much research and the new paper gave it some context.
“You can compare it to what happens in Australia with El Niño,” he said.
“It’s not quite equivalent but it’s the same story. You get a buildup of energy somewhere and that energy has to be dealt with.
“The net result is there’s this quite marked drying in parts of Chile.”
He said the rate of warming of that area of ocean showed what occurred when natural variation was combined with human-caused global heating.
“That’s the story of climate change,” he said.
“It’s quite amazing how much heat is being pumped into that ocean in that area east of New Zealand.”
Links
- New Zealand records seventh-hottest year, with extreme weather more likely
- New Zealand declares a climate change emergency
- From red seaweed to climate-smart cows: New Zealand leads the fight against methane
- Hot blob: vast patch of warm water off New Zealand coast puzzles scientists
- Chile's record-breaking drought makes climate change 'very easy' to see
- Climate change fueling warm ocean 'blob' causing Chile megadrought - study
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