Several thousand miles away, the South American nation of Chile has experienced a megadrought for more than a decade, with a declining supply of water and rain.
On the surface, these two events have nothing to do, but according to a new study, they are joined by invisible forces of global atmospheric pressure and circulation.
The Southern Blob, located in eastern Australia and New Zealand, emerged about four decades ago, probably caused by a natural drop in rainfall in the central tropical Pacific. But over time, climate change has made the Blob bigger and hotter, according to the study.
Falling rainfall affected atmospheric circulation in the region, creating wind patterns that changed the way cold, warm currents flow into the ocean, guiding more warm water toward the Blob as it pushes colder water further into low.
Then the warm water from the surface that makes up the blob heats the air above it and, as the atmosphere heats up, it expands into a “wide, wide area of high pressure. known as a high-pressure ridge, said Kyle Clem, co-author of the study and professor of climate science at Victoria University in Wellington.
This ridge, which stretches across the South Pacific, changes the path that storms usually take as they move across the oceans, known as “storm tracks.” Due to the ridge, storm systems shifted south into Antarctica and away from the west coast of South America.
The coastal region of South America, including central Chile, Argentina, and some parts of the Andes Mountains, relies on those winter storms to replenish freshwater supplies before the dry summer season. With storms now redirected to Antarctica, Chile has been plunged into severe drought conditions since 2010, with widespread damage to the environment and people’s livelihoods.
The study, published Thursday in the Journal of Climate, marks the first time researchers have made a direct connection between the Blob and the megadrought.
South America had previously seen a global decline in rainfall dating back decades, coinciding with the emergence of the Blob. But it was sporadic: sometimes there would be years of drought and other times of heavy rains.
But global warming has caused the Blob to expand and grow much more over the past decade, and the drought has become a continuous, endless stretch. During the winter season in the southern hemisphere, the Blob heats up about three times faster than the world average in other parts of the ocean, Clem said.
“So this started in the central tropical Pacific, warm up; the pattern continues for 40 years; then you only added heat by pumping into it because of the increase in greenhouse gases,” Clem said. “That’s what has allowed the Blob to reach such extreme warming rates … that’s why we see such an unprecedented drought.”
Prolonged drought has devastated farms across Chile, with crop failures and massive cattle deaths. Reservoirs are at critically low levels, and residents of some rural areas now rely on water supply from tanker trucks.
The shocking effects of the Blob have also been felt elsewhere. As the change causes warmer air to move to the Antarctic, it has led to a reduction in Antarctic sea ice, which in turn threatens the region’s delicate ecosystems and can have far-reaching consequences for the alteration. of global weather patterns.
It is unclear when or if the Blob will dissipate, which is what Clem and the team plan to study next. The drop in rainfall is expected to slow at some point, but researchers do not know if this will be enough to break the Blob or if it will be sustained only by the heat caused by humans.
“One of the most fascinating things about this is that we have this anthropogenic signal (caused by humans) in the climate system, which is the Blob, sitting in the middle of nowhere,” Clem said. “But because of the configuration of ocean circulations, it has the ability to influence the regional climates where large numbers of people live, tens of thousands of miles away.”
“What our study shows is that, with human-induced climate change, what happens in one place doesn’t necessarily stay there.”