If you saw the science fiction movie Arctic Blast, you might already know what a hole in the ozone is, and this report is not suggesting that the extreme events in the movie are related to this report or strictly factual. In case you are not familiar with ozone holes, the National Oceanographic and Atmospheric Administration (NOAA) has released information about the real hole in the Antarctic ozone and its implications.
Ozone is a gas that occurs naturally in very small quantities high up in the stratosphere. It forms a protective blanket for the earth that shields us from the sun’s dangerous ultraviolet (UV) radiation. This radiation can cause skin cancer in humans, as well as stopping plants from growing and other effects examined later in this article. The Antarctic ozone hole is the size of the United States and appears every spring, allowing some of the sun’s harmful UV rays to reach the earth’s surface. This year, according to NOAA, it reached its peak in September.
We have been hearing the warnings for years about the depletion of the ozone, but how many of us really understand the implications, and is it a real threat? The ozone layer helps protect the planet’s surface from harmful ultraviolet radiation. NOAA and NASA use balloon-borne instruments, ground instruments and satellites to monitor the annual South Pole ozone hole, global levels of ozone in the stratosphere and the manmade chemicals that contribute to ozone depletion.
Levels of Ozone
Depleting chemicals in the atmosphere have been gradually declining since an international treaty called the 1987 Montreal Protocol was signed to protect the ozone layer. That international treaty caused the phase-out of ozone-depleting chemicals, then used widely in refrigeration, as solvents and in aerosol spray cans.
In 1974, Nobel Prize-winning scientists Sherwood Rowland and Mario Molina posited that chlorofluorocarbons (CFCs) could deplete the stratospheric ozone layer. Subsequent research confirmed that commonly used chemicals – many of them components of everyday consumer products - were destroying the ozone layer. By 1985, scientists saw a drastic thinning of the ozone layer over Antarctica, an annual phenomenon dubbed the “ozone hole.” Research since then has deepened our understanding of the causes and dangerous environmental and human health consequences of ozone depletion, showing that effects appear not just at the poles but all over the world.
Scientists are now looking for signs that the ozone is healing, but the current data from Antarctica is not showing a reversal. The NOAA reports, “In August and September (spring in Antarctica), the sun begins rising again after several months of darkness. Circumpolar winds keep cold air trapped above the continent, and sunlight-sparked reactions involving ice clouds and manmade chemicals begin eating away at the ozone. Most years, the conditions for ozone depletion ease by early December, and the seasonal hole closes.”
Atmospheric models predict the Antarctic ozone hole will not close for one or two more decades, according to the latest analysis by the World Meteorological Organization, the 2010 Ozone Assessment, with co-authors from NOAA and NASA.
Tracking the Ozone Hole
This November is the 50th anniversary of the beginning of total ozone column measurements by the NOAA. The instrument station in the South Pole started taking measurements two decades before the Antarctic ozone hole began forming, which gives the scientists a unique opportunity to map the course of its formation and progress.
NOAA ESRL scientist Bryan Johnson helped co-author a recent NOAA paper that concluded it could take another decade to begin discerning changes in the rates of ozone depletion. Johnson is part of the NOAA team tracks ozone depletion around the globe and at the South Pole with measurements made from the ground, in the atmosphere itself and by satellite. Johnson’s “ozonesonde” group has been using balloons to loft instruments 18 miles into the atmosphere for 26 years to collect detailed profiles of ozone levels from the surface up. The team also measures ozone with satellite- and ground-based instruments.
Effects of Ozone Depletion
The U.S. Environmental Protection Agency outlines several areas of damage caused by ozone depletion, namely plants, marine ecosystems, biochemical cycles and manmade materials
Plants and Marine Ecosystems.
Physiological and developmental processes of plants are affected by UVB radiation, even by the amount of UVB in present-day sunlight. Despite mechanisms to reduce or repair these effects and a limited ability to adapt to increased levels of UVB, plant growth can be directly affected by UVB radiation, thus negatively impacting ecosystems.
In a study by the University of California at Santa Barbara, the thinning of the Antarctic ozone layer by as much as 50 percent, resulting in increased UVB radiation reaching the surface of the Southern Ocean, could affect the phytoplankton communities near the surface of the water, altering the dynamics of Antarctic marine ecosystems.
These changes can have important implications for plant competitive balance, plant diseases and biogeochemical cycles, reducing the survival rates for these organisms.
Solar UVB radiation has been found to cause damage to early developmental stages of fish, shrimp, crab, amphibians and other animals. The most severe effects are decreased reproductive capacity and impaired larval development. Even at current levels, solar UVB radiation is a limiting factor, and small increases in UVB exposure could result in significant reduction in the size of the population of animals that eat these smaller creatures.
These cycles are the flow of chemical elements and compounds between living organisms and the physical environment. Chemicals absorbed or ingested by organisms are passed through the food chain and returned to the soil, air and water by such mechanisms as respiration, excretion and decomposition. As an element moves through this cycle, it often forms compounds with other elements as a result of metabolic processes in living tissues and of natural reactions in the atmosphere, hydrosphere or lithosphere.
Increases in solar UV radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering sources, greenhouse gases and chemically important trace gases, including carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulfide (COS) and possibly other gases, including ozone. These potential changes would contribute to biosphere-atmosphere feedbacks that reinforce atmospheric buildup of these gases.
Effects on Materials
Synthetic polymers, naturally occurring biopolymers, as well as some other materials of commercial interest, are adversely affected by solar UV radiation. Today's materials are somewhat protected from UVB by special additives. Therefore, any increase in solar UVB levels will therefore accelerate their breakdown, limiting the length of time for which they are useful outdoors.
Montreal Protocol Not Enough
In an article in 2009 in the New York Times, ”government scientists who study the depletion of Earth’s protective ozone layer are pointing to a previously unheralded culprit: nitrous oxide. It is not regulated under the Montreal Protocol.
Most of the nitrous oxide in the atmosphere emerges naturally, through the action of bacteria in the soil, the researchers say. But the gas is also produced by human activity through the use of nitrogen-based fertilizers, the application of livestock manure to fields, the burning of biofuels and in other ways.”
With the proliferation of nitrogen-based chemical fertilizers being used worldwide, this is a concern. In addition, the fumigant methyl bromide used in agriculture as well needs to be eliminated.
The Environmental Protection Agency considered action at the time on nitrous oxide because it is a heat-trapping gas linked to global warming. Earlier that year, the agency declared it and five other gases, including carbon dioxide, to be pollutants that endanger public health, making them subject to regulation under the Clean Air Act.
Ecosystem stress, loss of diversity, damage to ecosystem structure and loss of balance to plant and aquatic systems due to shifting natural relationships can be the result of ozone depletion, allowing increasing levels of UVB radiation. These effects are particularly devastating to endangered species and sensitive ecosystems and how they interact with humans through the food chain.
Upon the 20th anniversary of the Montreal Protocol, the Environmental Protection Agency concluded, “The global success of the Montreal Protocol stands out as an ever-more significant landmark of international cooperation to avert severe environmental consequences. Major challenges remain, including the final phase-outs of key chemicals that damage the ozone layer, including the agricultural fumigant methyl bromide. In all these areas, decisive leadership has been vital to U.S. contributions to the global success of the Montreal Protocol. Continuing success in completing the important agenda of future work that faces the Parties will rely just as heavily on partnerships, vision and the willingness to make difficult decisions and implement them rigorously.”
POSSIBLE EFFECTS OF OZONE DEPLETION ON THE GLOBAL CARBON CYCLE; TSUNG-HUNG PENG; Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831; USA
New York Times
National Oceanographic and Atmospheric Administration