That in turn strengthens the polar vortex, which drives a positive SAM, promoting increased rainfall in south-eastern Australia. The ozone hole causes a stronger polar vortex and a stronger polar vortex causes a bigger hole in the ozone layer. Ozone intercepts the sun's heat and keeps it in the stratosphere, so if there's less ozone, then temperatures in the stratosphere can be colder than average, intensifying the polar vortex. With ozone-depleting chemicals inside the polar vortex, under certain conditions, the ozone hole can get bigger. Since ozone-depleting chemicals like CFCs began being phased out in 1987, the hole in the ozone layer has been healing.īut ozone-depleting substances will remain for decades to come. "And so you have this unique environment for the ozone destruction to occur." Loading "And one of the reasons that we have these chemical reactions over Antarctica is the strong polar vortex is so fast that it isolates the Antarctic air from the rest of the atmosphere.
"In springtime, over Antarctica, because there are human-emitted ozone-depleting chemicals … you start to get chemical reactions that destroy the ozone high up in the atmosphere," Dr Purich said. So how could smoke strengthen the polar vortex? Ozone hole, polar vortex and SAM are all linked Scientists have attributed that to bushfire smoke," Dr Jucker said. "Just a year after this extremely weak polar vortex in 2019, it was extremely strong in 2020. That stratospheric smoke drifted south all the way to Antarctica. The bushfires were so intense that millions of tonnes of smoke were injected up to 35km into the sky, high into the stratosphere. "The strong El Niño event in the central Pacific Ocean during spring 2019 is also likely to have influenced the sustained negative SAM at that time," Dr Marshall said.īushfire smoke affected the global climate Over the following weeks and months, the effects reached the Earth's surface, leading to westerly winds moving north over Australia - the reverse of what's happening right now. "In 2019, the polar vortex winds, which are usually very strong, became extremely weak," said climate scientist Martin Jucker, an expert in sudden stratospheric warming from the University of New South Wales.Īt the time, scientists from the BOM warned the rare event could intensify the drought. If the temperatures above the pole warm, then the polar vortex can weaken. The polar vortex, which spins at up to 200 kilometres an hour, is powered by the difference in temperature between the pole, which sees little sun, and the Southern Ocean, which is warmed by the sun. This warm air, up to 35 degrees Celsius above normal, broke down the polar vortex. They're effectively random and are quite rare in the Southern Hemisphere.
These events aren't caused by global warming. The atmosphere above the South Pole abruptly began rapidly heating in an event called sudden stratospheric warming. In September 2019, something very strange occurred over Antarctica.
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