December 1, 2021

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How does a "hot spot" near New Zealand contribute to the drought in Chile and Argentina?  Ecology |  Magazine

How a “hot spot” near New Zealand contributes to the mega drought in Chile and Argentina | Ecology | Magazine

The southern part is not the hottest part of the ocean, as the tropics are much warmer, a study reveals.

A tropical zone in the western South Pacific has been responsible for the mega-drought that has plagued Chile and western Argentina since 2010, according to a new study.

Scientists have given this sea area near New Zealand a colloquial name and are similar to Australia: they call it “Warm place“Oh”Southern location”.

This area is warmer than its surroundings due to a natural phenomenon, the researchers clarify. But its unusual duration and severity are linked to climate change..

The study, by scientists from Chile and New Zealand, was published in the journal Climate Magazine From the American Meteorological Association.

Four times the heat

“All parts of the ocean are warming, but the southern part is isolated because at least the southern hemisphere has the maximum warming,” said Ren சில Carrot, a Chilean climate expert who led the study.

CR2 is a professor of geophysics at the University of Chile and deputy director of the Center for Climate and Recession.

Chilean climate expert Rene Carrot. Gentleisa Rene Karyat

The southern part is not the hottest part of the ocean, as the tropics are much hotter. But that’s the basic thing for researchers Heat rate.

“We focus on long-term trends, 40 years.”

“To give you an idea, the ocean warms on average one tenth of a degree per decade, but this area is warming 0.4 degrees per decade, which means in 40 years it has warmed by 1, 5 or 1.6 degrees.

This is four times the warming rate of your environment In the same latitudes as in the Pacific, Atlantic or Indian Ocean ”.

Southern Point and Climate Change

Hot sea spots called in English BubblesOh Ocean heat waves (Ocean heat waves), is a natural phenomenon already known to scientists.

But those spots are usually temporary and can last a year or two.

Part of Lake Penulas in the Valparaiso area in January 2020. Getty Images

“A sea heat wave was recorded in California a few years ago,” Garrett said.

“Suddenly there are a lot of those places on the Atlantic coast of South America. You see hot places that last for a few months and then scatter.”

“This is an unstable phenomenon associated with ocean currents.”

However, the location is close to New Zealand This is very unusual because it has been around for 40 years.. One of the big questions is whether this period can be due to climate change.

“We know from simulations that the southern hemisphere can occur in the natural world (by human action) without the anthropological effect of climate change, but the rate at which it warms is much higher than we have seen in prehistoric times.

“It leads us to two things. One is that stains can occur naturally. Second, climate change is pushing it forward, so the Pacific region is warming faster.”

La Manza, “responsible for the Great Drought”

Garrett confirmed that “the stain now appears to be the most direct cause of the great drought in South America.”

Impact of a major drought in the El Melon region of Chile in 2020. Getty Images

“The test one can do on a sample is: ‘Let’s remove the stain and let the sea be normal in that area.’ When you do this experiment on a numerical model, you find that the drought is reduced by more than 70%.

“I will say it Three-quarters of the drought is due to the presence of stainsIn other words, the stain plays a very important role. “

In Chile, a severe drought is affecting the central part of the 1,000-kilometer-long country. It stretches about 500 km north of Santiago and about 500 km south.

In the western region of Argentina, the drought affects the region of Mendoza and Cuo.

From stains to dryness: gradually

If so, what is the sequence of events that link the location near New Zealand to the drought in South America?

“It starts with the stain, which warms the ocean. That heat is transferred to the atmosphere, So the whole area above the stain is hot, it’s like you put a small flame underneath, in this case the stain, ”Karate began.

Temperature also goes hand in hand with atmospheric pressure, And as the wind blows from Australia to South America, that high temperature eventually turns into more pressure Expanding across the PacificHe continued.

“What it’s doing when it expands is intensifying an area that will always be there, which is the Pacific anticyclone.”

The Pacific Anticyclone This explains why Santiago’s climate on the coasts of South America is generally drier than Montevideo, although both cities are at the same latitude.

But when it becomes more intense due to the effect of the stain, anticyclone Prevents the arrival of storm surges or front systems To the central part of Chile, Cordillera and western Argentina.

Due to the sequence of events starting at that location, the storm surges did not reach central Chile and western Argentina. Gentleisa Rene Karyat

In very simple terms, Garrett explained that the anticyclone is an air descent zone.

“Anticyclone is a component of high pressure and it is formed by the descent of air, and when it rains it is the opposite: the moisture condenses and eventually rises to fall”.

“If you have these conditions that crush the atmosphere – I say it very colloquially – of course you are very unlikely to create cloud and rainfall systems.”

In central Chile, unlike western Argentina, there is no summer rain.

“So our only chance is window systems, storm surges, in the winter,” he continued.

“But with the increase in stains and pressure that has heated the atmosphere, the anticyclone has become more intense and closed the door to front systems that could have reached central Chile.”

Storm nodes not reaching the central part of Chile Moving further south.

Areas of Magallanes and Dierra del Fuego have received increased rainfall, which may be due to this deviation, Carate explained.

“Even part of the Antarctic Peninsula has received more westerly winds and eventually more rain. The stain may have played a part there.”

Impact of mega drought

The current drought in Chile for more than a decade is very different than it was in the past.

“Our country has always had droughts and they are most severe in Mediterranean climates like California, South Africa, Australia.”

“But Drought lasts from one to two years“Carrot explained.

The mega-drought-stricken central region “is home to 70 or 80% of Chile’s and a good portion of agriculture, industry, trade, and some mining.”

The province of Mendoza in Argentina was severely affected by the drought. Getty Images

On the other hand, water consumption is increasing. “So you have a low supply and at the same time a high demand, which is a bad recipe.”

“To give you an idea, the average deficit is consistently 30%, i.e., We live one-third less than the average between 1980 and 2010”.

“In Santiago, for example, we have an average size of 330mm, which is not much. We have been below 250mm for so many years since 2010.”

Natural variation + climate change

James Renwick, a non-research scientist, heads the Department of Geography, Environment and Geosciences at Victoria University in Wellington, New Zealand.

Renwick, who surveyed the south, told BBC Mundo that the study’s best contribution was to show “the combination of natural variation with continuous warming and climate change caused by greenhouse gas emissions.”

“In hotspots and South American climates its effects can occur naturally without any human assistance,” Renwick said.

“But the study clearly shows that climate change has increased the area’s warming Its effects have also increased in Chile due to climate change”.

“The biggest peaks we experience from climate change occur when the natural variation of climate is combined with background warming.”

New Zealand meteorologist Kyle Clem told BBC Mundo, another author of the study, “Growth in the south seems to have a natural effect on reducing rainfall in the tropical central Pacific.

“Therefore, Natural climate change and anthropological climate change have come together It has caused such intense sea warming in the last 40 years, ”Clem said.

“It has created a high pressure zone, which explains the unprecedented nature of the drought in central Chile.”

“Expectation of the Future”

Carrot and his colleagues still have many questions to answer about the Southern stain.

“So far we have only seen the surface of the stain … yet we know that the Pacific region is accumulating more heat in the first few hundred meters.”

“In addition, Million dollar question The size of the stain is ‘natural’ in appearance (and ultimately reversible) and what (and how) the contribution of climate change tends to maintain the stain ”.

“This division is not just a matter of scientific interest. Your response will tell us the duration of this event and its fate in the decade in which we began. ”

Lake Agulio, 70 km southwest of Santiago in 2019. Getty Images

The big question for many in Chile is how long the mega drought will last.

“One can reasonably expect more or less the next few decades, Now and between 2030 and 2040, we will definitely get a little reversal Towards a slightly more humid environment. Since part of the stain looks natural and that part eventually disappears, natural things have cycles and they go back and forth, ”Garrett explained.

However, the scientist later said over time, “In the middle of the century, In 2050, 2060, we call it a mega drought today. This situation is not news because it will be a permanent regime.”.

“The tail of climate change is already there, so I’m not expecting things to return to what they were in the ’80s or’ 90s, depending on rainfall. Unlike other places like Uruguay or central Argentina, the future in central Chile will be dry and hot, with rain and heat.”

“So to Central Chile Mega drought is a preview of the future. The future was ahead of us as the signal of climate change mixed with the signal of natural variation. ” (I)

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