A combination of extreme cold temperatures, man-made
chemicals and a stagnant atmosphere were behind what became known as the Arctic
ozone hole of 2011, a new NASA study finds.
Even when both poles of the planet undergo ozone losses
during the winter, the Arctic’s ozone depletion tends to be milder and
shorter-lived than the Antarctic’s. This is because the three key ingredients
needed for ozone-destroying chemical reactions —chlorine from man-made
chlorofluorocarbons (CFCs), frigid temperatures and sunlight— are not usually
present in the Arctic at the same time: the northernmost latitudes are
generally not cold enough when the sun reappears in the sky in early spring.
Still, in 2011, ozone concentrations in the Arctic atmosphere were about 20
percent lower than its late winter average.