The Antarctic ozone hole reached its annual maximum in September to become the fifth largest hole in recorded history.
- You're looking at the fifth-largest Antarctic ozone hole in modern times. Also shown are holes from 1981 and 1991. (NOAA / Environmental Visualization Lab)
It has been an odd year at the planet's poles.
Over at Santa's crib in the North Pole, a totally new and unexpected breach developed in the stratosphere. Scientists believe that this first-ever Arctic ozone hole was caused by an unusually long period of cold temperatures last winter, cold being one thing that helps tear ozone molecules apart. The unprecedented level of depletion of ozone is not good news, because 1) ozone is what blocks cancer-causing UV-B rays from making it to the earth's surface, and 2) the Arctic hole floats over densely populated areas up north, frizzling lifeforms below with space radiation.
Down at the South Pole, there's also strange things brewing. The Antarctic ozone hole spread to humongous proportions this year, ranking as the fifth-largest Antarctic breach in modern times. At its maximum size on Sept. 14, the hole covered nearly 9.7 million square miles. Compare that to the largest known ozone gulf above the South Pole, which opened up in 2006 and measured 20.6 million square miles.
The size of Antarctic hole has leveled off since countries around the world banned ozone-depleting CFCs with the 1989 Montreal Protocol. But it can still swell up suddenly from year to year. And while there's not a lot of people living in Antarctica getting UV-blasted by this thing, the hole does have a baleful effect on living things. According to the National Science Foundation:
During this period, increased intensity of ultraviolet radiation has been correlated with extensive DNA damage in the eggs and larvae of Antarctic fish. Embryos of limpets, starfish, and other invertebrates do not grow properly. Other species have developed defenses. The Antarctic pearl wort, a mosslike plant on rocky islands, developed a pigment called flavenoid that makes it more tolerant of ultraviolet radiation.
The graphic you see above, made by NOAA's mad modelers, shows in red where the ozone concentration fell below 220 Dobson units at the hole's maximum in September. For comparison, the maximum holes from 1981 and 1991 are also shown. The void usually starts to close up again around November. You can keep a daily bead on it by visiting NASA's Ozone Watch for fascinating graphics and even movies of the shifting hole.