February 9, 2013
Hole In Antarctic Ozone Layer May Be On The Mend
April Flowers for redOrbit.com - Your Universe Online
According to satellite data, the most recent hole in the ozone layer measured over Antarctica was the smallest it has been in ten years. Other long-term research studies also indicate that the Earth's ozone layer seems to be on the mend thanks to international agreements to protect this vital layer of the atmosphere.
Continuing the work started by ERS-2 and Envisat satellites, imaging from the European Space Agency´s (ESA) MetOp weather satellite showed the yearly hole over Antarctica to be at its smallest size in over a decade.
Each year since the late 1980s, an ozone hole has developed over Antarctica during spring in the southern hemisphere, which decreases the ozone concentration by up to 70 percent. South of the equator, spring generally lasts from September to November. During this time, high-speed winds create a rapidly rotating vortex of cold air, which leads to extremely low temperatures and more rapid ozone depletion than what occurs at the North Pole.
In the arctic regions north of equator, the effects of ozone thinning are far less dramatic because the northern hemisphere´s irregular landmasses and mountains usually prevent the build-up of strong winds.
Human-made chlorofluorocarbons (CFCs) have a stronger effect on the ozone under the conditions found in the southern hemisphere, creating the infamous "ozone hole." Populations of people living south of the equator have been found to experience higher rates of cancer due to exposure to increased levels of ultraviolet radiation.
International agreements such as the Montreal Protocol of 1989 have put restrictions on the use of CFCs in products and dramatically curbed their concentrations in the atmosphere, which have been recorded on a yearly basis since the mid-1990s. However, CFCs have a long lifetime in the atmosphere, and experts say that it may take until the middle of this century before the stratosphere's chlorine content returns to pre-1960's values.
The interplay between atmospheric chemistry and environmental factors such as wind and temperature affects the evolution of the ozone layer. Extreme ozone conditions — such as the record loss of ozone observed in the 2011 spring season in Antarctica — can also partly result from unusual weather and atmospheric patterns.
Scientists have relied on a long-term series of data obtained from observations and results from numerical simulations and complex atmospheric models to understand these processes better. The ozone has been studied and observed for several decades now using a variety of instruments. Nevertheless, combining observations from different types of instrumentation to create a consistent and homogeneous data set for analysis has proven a challenge.
The ESA Climate Change Initiative has allowed ozone climate data records to be harmonized, documenting the variability of ozone changes better at different scales in space and time. This new information has allowed researchers to better estimate the timing of ozone layer recovery and, in particular, the closure of the ozone hole.
Researchers using chemistry climate models have shown that the ozone layer appears to be recovering and estimates that the ozone hole could close entirely in the next few decades.