It is a major problem, which does not seem to have a quick solution. In Chile, the megadrought affects the central region of the country. It is a strip of 1,000 kilometers. It extends about 500 km north from Santiago and about 500 km south. The western region of Argentina is also affected by this phenomenon. What causes the megadrought in Argentina and Chile?
The hot spot
It is caused by a warm area in the western South Pacific. An oceanic area that is near New Zealand and is similar in size to Australia. They call it the “warm spot” or “southern spot” (hot blob). This area warmer than its surroundings is partly due to a natural phenomenon. But its unusual duration and intensity is related to climate change.
The study was done by scientists from Chile and New Zealand. It was published in the journal Journal of Climate of the American Meteorological Society. “The warming there, at least in the southern hemisphere, is the maximum.” Says Chilean climatologist René Garreaud, lead author of the study. He is a professor in the Department of Geophysics at the University of Chile.
The southern blob is not the warmest part of the ocean. Tropical areas are much warmer. But the key thing for researchers is the rate of warming. “On average the ocean is warming at a tenth of a degree per decade. But this area is warming at about 0.4 degrees per decade.”
Unusual permanent warmth
Oceanic warm spots are a known natural phenomenon. They are usually transient and last about a year or two. However, the spot near New Zealand is extremely unusual. It’s been there for 40 years now. And one of the big questions is whether this duration could be due to climate change. “Climate change is giving it a push forward.”
Knowing this, it’s clear what’s causing the mega-drought in Argentina and Chile. “A model was made. In this one, there was no stain. The drought decreases more than 70%.”
“A surface heats up in the ocean. That heat is transferred to the atmosphere. The whole area above the spot is warmer. Temperature also goes hand in hand with atmospheric pressure. Winds blow from Australia towards South America. Then that higher temperature spreads out across the Pacific,” he continued. “As it arrives, it intensifies an area that’s always been there. The Pacific anticyclone.
The dry future
What happens as it becomes more intense due to the effect of the stain? It prevents storm fronts from reaching central Chile, the Cordillera and western Argentina. These are being diverted further south. The area of Magallanes and Tierra del Fuego have had an increase in precipitation. This explains it.
“For now we’ve only looked at the surface of the slick. We know that that area of the Pacific is accumulating a lot of heat in the first few hundred meters,” says Garreaud.
The big question for many in Chile is how long the megadrought will last. “Towards the middle of the century, in 2050, 2060, this condition that today we call the megasequia is not going to be news. Because it is going to be the permanent regime.
“So for central Chile the megasequia is a foretaste of the future. It’s like the future is ahead of us. Because the signal of climate change was mixed with the signal of natural variability”.