Naaju Breaking News, Live Updates, Latest Headlines, Viral News, Top Stories, Trending Topics, Videos
[ad_1]
A warm area in the western South Pacific is partly behind the mega-drought that has affected Chile and western Argentina since 2010, according to a new study.
Scientists have given this ocean area near New Zealand and similar in size to Australia a familiar name: they call it the “hotspot” O “south point” (hot drip, in English).
This area, which is warmer than its environment, is partly due to a natural phenomenon, the researchers say. But its unusual duration and intensity are linked to climate change.
The study, conducted by Chilean and New Zealand scientists, was published in the journal Climate Journal from the American Meteorological Society.
Four times hotter
“All parts of the ocean have warmed up, but the southern part stands out because there has been a warming which at least in the southern hemisphere is the maximum,” said Chilean climatologist René Garreaud, lead author of the study.
Garreaud is Professor in the Department of Geophysics at the University of Chile and Deputy Director of the Center for Climate and Resilience, CR2.
The location to the south is not the hottest part of the ocean, as the tropics are much warmer. But the fundamental thing for researchers is the heating rate.
“We are focusing on long term trends over 40 years.”
“To give you an idea, on average the ocean warms by a tenth of a degree per decade, but this area is warming by about 0.4 degrees per decade, which means that in 40 years it has warmed. is heated by 1, 5 or 1.6 degrees “.
“It’s about four times the rate of warming in your environment at the same latitudes in the Pacific, Atlantic or Indian Oceans.
The southern spot and climate change
Hot oceanic plates, called blobso marine heat waves, are a natural phenomenon already known to scientists.
But these spots are usually temporary and last for about a year or two.
“An ocean heat wave was recorded off the coast of California a few years ago,” Garreaud said.
“And suddenly there are a lot of these spots off the Atlantic coast of South America, you see hot spots that last a few months and then dissipate.”
“It’s a transient phenomenon that has to do with ocean currents.”
However, the place near New Zealand It is extremely unusual as it has been around for 40 years.. And one of the big questions is whether this duration could be due to climate change.
“We know, based on simulations, that the southern spot can occur in a natural world, without the anthropogenic (human-made) effect of climate change. But the rate at which it warms is much higher. than the one we have seen. in prehistoric times.
“This leads us to conclude two things. One is that the stain can occur naturally. The second is that climate change is giving it a boost, causing this region of the Pacific to warm faster.”
La Mancha, “responsible for the mega-drought”
Garreaud said that “the stain now appears to be a very, very direct culprit” for the mega-drought in South America.
“The experience you can have in a model is to say, ‘Let’s remove the stain, let’s let the ocean be normal in this area.’ When you do this experiment in a digital model, you see that the drought decreases by over 70%. ”
“I would say that at least three-quarters of the drought is mainly due to the presence of the stain, in other words, the stain has a very, very, important role. ”
In Chile, the mega-drought affects the central region of the country, a strip of 1000 kilometers. It stretches for about 500 km north of Santiago and about 500 km to the south.
In the western region of Argentina, drought affects the region of Mendoza and Cuyo.
From stain to drought: step by step
So what is the sequence of events that connects the place near New Zealand to the drought in South America?
“It starts from the stain, a warming surface in the ocean. This heat is transferred to the atmosphere, so the whole area above the stain is hotter, it’s like putting a little flame underneath, which in this case is the stain, ”Garreaud began.
“Temperature also goes hand in hand with atmospheric pressure, and also as the winds blow from Australia to South America, this higher temperature which ultimately results in higher pressure stretches across the pacific“He continued.
“And what it has done as it expands is intensify an area that has always been there, which is the Pacific high.”
The Pacific high pressure on the coasts of South America, this is what normally explains, for example, that the climate of Santiago is much drier than that of Montevideo, although the two cities are at similar latitudes.
But as it becomes more intense due to the effect of the spot, the high pressure prevents the arrival of storm fronts or frontal systems in the central region of Chile, the Cordillera and western Argentina.
Garreaud explained that, in very simple terms, a high pressure area is an area of descent of air.
“A high pressure area is an area of high pressure and it originates because the air goes down, whereas to rain it is the opposite: it rises so that the humidity condenses and finally precipitates.”
“If you have these conditions that crush the atmosphere – I say this in a very familiar way – of course you are very unlikely to have cloud and precipitation systems developing.”
In central Chile, unlike western Argentina, there is no summer rains.
“So our only window of opportunity is for frontal systems to come, storm fronts, in winter,” he continued.
“But with the stain that warmed the atmosphere and the pressure increased, the high pressure system is more intense and closed the door to frontal systems that could have reached central Chile.”
Storm fronts that do not reach the central region of Chile drift further south.
The region of Magallanes and Tierra del Fuego has seen an increase in precipitation which could be in part due to this difference, explained Garreaud.
“Even part of the Antarctic Peninsula received more westerly winds and possibly more precipitation. The stain could play a role.”
The impact of the mega-drought
The current drought of more than a decade in Chile is very different from others of the past.
“Our country has always known droughts and they are very intense as in Mediterranean climates, such as California, South Africa, Australia.”
“Corn droughts lasted one to two yearsGarreaud explained.
The central region affected by the mega-drought is also “the area where 70% or 80% of Chileans live and where a good part of agriculture, industry, commerce, part of mining is concentrated” .
On the other hand, water consumption is increasing. “So you have less supply and at the same time more demand is a bad recipe.”
“To give you an idea, persistently the average deficit was 30%, that is to say we live on a third less than what we had on average between 1980 and 2010. “
“In Santiago, for example, we’re used to having an average of 330mm, which isn’t much either, and all these years from 2010 onwards we’ve been below 250mm.
Natural variability + climate change
Scientist James Renwick, who was not involved in the study, heads the Department of Geography, Environment and Earth Sciences at Victoria University in Wellington, New Zealand.
Renwick, who studied the southern patch, told BBC Mundo that a very good contribution of the study is to show “a combination of natural variability with continued warming and climate change caused by the emission of greenhouse gases. Greenhouse”.
“The hotspot and its effects on the South American climate can occur naturally without any human assistance,” Renwick said.
“But the study clearly shows that the warming of the place has been increased by climate change, and therefore its effects in Chile have also increased due to climate change. “
“The greatest extremes we are experiencing as a result of climate change occur when natural variation in climate adds to background warming.”
New Zealand climatologist Kyle Clem, another of the study’s authors, told BBC Mundo that “the development of the southern spot appears to have a natural origin linked to reduced precipitation in the tropical central Pacific. But warming of the ocean has been intensified by increasing greenhouse gas emissions ”.
“So, natural climate variability and anthropogenic climate change have combined over the past 40 years to cause such extreme warming of the oceans, ”added Clem.
“And this produced an area of high pressure which explains the unprecedented nature of the drought in central Chile.”
“An anticipation of the future”
There are many questions that Garreaud and his colleagues are still trying to answer about the southern spot.
“So far we’ve only looked at the surface of the spot … although we know that this area of the Pacific accumulates a lot of heat in the first few hundred yards.”
“As well as, the million dollar question is the share of the spot of “natural” (and possibly reversible) origin and what (and how) is the contribution of climate change which tends to maintain the spot ”.
“This score is not just a scientific curiosity. Your answer could inform us about the duration of this phenomenon and its fate in the decade that we have started.”
The big question for many in Chile is how long will the mega-drought last.
“One could more or less reasonably expect that in the coming decades, by 2030, 2040, we will surely have a little turnaround to slightly wetter conditions. Because part of the stain is of natural origin and that part will eventually disappear, natural things have cycles and they come and go, ”explained Garreaud.
However, the scientist pointed out that later in time, “around the middle of the century, in 2050, 2060, this condition which we call today the mega-drought will not be relevant because it will be the permanent regime “.
“The tail of climate change is already here, so I don’t expect things to go back to how they were in the 80s or 90s in terms of precipitation. The future is going to be dry and hot in central Chile. unlike other places such as Uruguay or the central zone of Argentina where it will be rainier and warmer. ”
“So for central Chile mega-drought is a foretaste of the future. As the future was before us because the signal of climate change mingled with the signal of natural variability “.
.
[ad_2]
Source link
