Ozone Hole over Antarctica
Life at the margins may be extreme, but it is also fragile. The British Antarctic Survey's first documentation of the Antarctic ozone hole in 1985 and subsequent NSF-funded study of the phenomenon alerted the world to the danger of chlorofluorocarbons, or CFCs. That research team, led by recent National Medal of Science winner, Susan Solomon, conducted observations that have significantly advanced our understanding of the global ozone layer and changed the direction of ozone research.
Stratospheric ozone protects against ultraviolet radiation. The breakdown of this ozone layer by CFC molecules can have harmful effects on a range of life forms, from bacteria to humans. The long, cold, dark Antarctic winters allow the formation of polar stratospheric clouds, the particles of which form an ideal surface for ozone destruction. The returning sunlight provides energy to start the complex chemical reaction that results in ozone destruction. The ozone hole above Antarctica typically lasts about four months, from mid-August to late November.
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.
In the northern polar regions, ozone levels in the early 1990s measured ten percent lower than those estimated in the late 1970s. The Arctic does experience ozone depletion, but to a lesser degree than the Antarctic. Unlike the Antarctic, large-scale weather systems disturb the wind flow in the Arctic and prevent the temperature in the stratosphere from being as cold. Therefore fewer stratospheric clouds are formed to provide surfaces for the production of ozone-depleting compounds. Some clouds do form, however, and allow the chemical reactions that deplete ozone. Ozone depletion has a direct effect on human inhabitants, but research has only just begun on the effects of increased ultraviolet radiation on terrestrial and aquatic ecosystems and societies and settlements in the Arctic.
The good news is that countries around the world have agreed to ban the manufacture of CFCs through the Montreal Protocol. The contributions of Antarctic researchers led to swift policy action and because of that the ozone layer should recover in the future. In the meantime, however, NSF-funded research continues to monitor the level of the CFCs still lingering in the atmosphere. The polar regions will continue to play an important role as early warning systems for the rest of the globe.