Victoria University of Wellington School of Geography, Environment and Earth Sciences lecturer and research co-author Dr Kyle Clem said it was unclear when, or if, The Blob would dissipate, given it had formed as a result of human-induced climate change.
It covers about 8 million sq km and was only discovered after studying the year-after-year drought conditions in central South America, and the strong, continuous warming of upstream ocean waters in the South Pacific.
Clem said computer models, which did not account for anthropogenic greenhouse gas emissions, managed to replicate The Blob and show a connection to a decline in convection in the central tropical Pacific.
"It is clear that winter storm systems, which deliver the majority of annual rainfall in this Mediterranean climate, were moving south towards Antarctica and being replaced with a large ridge of warm and dry high pressure, extending from New Zealand to the central South American coast.
"The Blob has blocked winter storms from reaching the subtropical west coast of South America, a region that relies on these storms to replenish freshwater sources before the summer dry season.
"This mega-drought has dwindled freshwater supplies across central Chile, affecting drinking water in rural communities, hydro-generation, agriculture, and many other activities in a highly populated area that includes the capital city of Santiago."
He said in some years, rainfall had been as low as 30 per cent of normal, and rainfall figures show 2021 would be another very dry year.
"What our study shows is that, with human-induced climate change, what happens in one place does not necessarily stay there.
"The Southern Blob, though likely natural in its formation, has reached extreme levels of warming due to increasing greenhouse gases, with cascading effects on the climate system across the Southern Hemisphere affecting millions of people, seemingly far-removed geographically from the source."
