The smaller ozone hole in 2017 was strongly influenced by an unstable and warmer Antarctic vortex
- the stratospheric low pressure system that rotates clockwise in the atmosphere above Antarctica.
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.
In comparison, the Antarctic vortex
is very stable and lasts until the middle of spring.
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