In comparison, the Antarctic vortex
is very stable and lasts until the middle of spring.
This is because the Arctic polar vortex, a persistent large-scale cyclone within which the ozone loss takes place, was about 40 percent smaller than a typical Antarctic vortex
The amount of ozone lost so far this year already exceeds the total lost in 1988, a year when several large weather patterns formed in the Southern Hemisphere and disturbed the Antarctic vortex
-- a ring of winds circling the pole that seal off the Antarctic stratosphere.
The method works inside the Antarctic vortex
because ozone levels there drop to extremely low values.
Researchers who believed that chemistry was the driving force behind the ozone hole had originally assumed that unusual chemical conditions would extend throughout the entire Antarctic vortex