Unprecedented hole opened up in Antarctic winter sea ice

The Antarctic ozone hole reached its largest size ever observed in September, expanding to 10.6 million square miles (27.4 million square kilometers). This year's hole is the second-biggest since the monitoring began in 1979. The ozone layer, which protects life on Earth from harmful ultraviolet radiation, was supposed to be healing after the 20th-century damage caused by human-made chemicals.

However, this year's hole is so large that some experts believe it could be the start of a new long-term trend of persistent, large holes. The ozone hole forms every year during the Southern Hemisphere's winter and spring, reaching its maximum size between mid-September and early October. It then shrinks until late January. The hole's size is influenced by extremely low temperatures in the stratosphere, which trigger the formation of high-altitude clouds that convert chlorine into its ozone-destroying form.

This year's large ozone hole is caused by a very strong polar vortex, which created colder-than-usual conditions in the stratosphere over Antarctica and accelerated the growth of the hole. While scientists don't detect an increase in reactive chlorine, the colder polar vortex has triggered more ozone depletion than usual. However, it's unlikely that this year will break the 2015 record, as the hole is shrinking since September 20.

Researchers believe that the ozone hole will remain large and fluctuate over the next few weeks, but it's essential to keep a close eye on the situation.