According to the United Nations Weather Agency, the ozone layer covering the Arctic has thinned by 40 percent this past winter. This sets a new record for ozone layer loss; previous seasonal loss has only been approximately 30 percent. According to Bryan Johnson, an atmospheric chemist who works in the U.S. National Oceanic and Atmospheric Administration’s Earth System Laboratory, the drop in ozone layer is “sudden and unusual.” Johnson went on to say that despite the ozone layer’s ability to regenerate itself, a consistently large drop in ozone levels could mean “a trending downward of the atmospheric ozone layer.” Observations from the ground and from balloons over the Arctic, in addition to satellites, have all indicated that the ozone layer has suffered a dramatic loss from the beginning of winter to late March.
The atmosphere’s ozone layer is located in the stratosphere. The stratosphere is the second layer of the atmosphere and accounts for approximately 90% of the ozone in the atmosphere. The stratosphere starts at an altitude of about 10 kilometers and reaches to about 50 kilometers altitude.The ozone layer is responsible for absorbing ultraviolet light, protecting life on Earth from harmful UV radiation from the sun.
Several factors have contributed to the loss in the ozone layer’s atmospheric layer. The U.N.’s World Meteorological Organization has pointed to a combination of cold temperatures in the stratosphere and the contribution of chlorofluorocarbons (CFCs) from humans. Michel Jerraud, the secretary general of the U.N. Weather Agency, pointed out that despite the Montreal Protocol, the ozone layer over the Arctic “continues to be vulnerable to ozone destruction caused by ozone-depleting substances linked to human activities,” such as aerosol sprays and refrigerators.
The 1987 Montreal Protocol called for the world’s countries to reduce the amount of CFCs used in the manufacturing of air conditioning, aerosol sprays, and other products. Because CFCs have long lifetimes in the atmosphere, though, it will take decades for the ozone layer to return to the levels it experienced before 1980. Estimates for the return to pre-1980 levels in the polar region are projected to occur between 2030 and 2040. The World Meteorological Organization has acknowledged that “without the Montreal Protocol, this year’s ozone destruction would most likely have been worse.” Had the Montreal Protocol not been adopted, two-thirds of the world’s ozone layer would be gone within the next fifty years. Global temperatures would also have risen several degrees due to CFCs.
The cold temperatures degraded the ozone layer by allowing iridescent ice clouds to form over the polar region when the temperature falls below -108 degrees Fahrenheit. When rays from the sun make contact with an icy surface, ozone-eating reactions in chlorine and bromine are triggered. These elements are present from the production of CFCs, which are commonly found in refrigerants and flame retardants in household supplies. Despite the unusually cold temperatures in the stratosphere over the Arctic this year, ground temperatures were significantly warmer this winter.
Ozone levels in the Arctic region vary more than those near the South Pole due to the fact that temperatures are always warmer in the Arctic. The fluctuation in temperatures and seasonal conditions greatly influence the ozone levels; there have been years where there is almost no ozone loss, and other years, including 2011, where cold stratospheric temperatures contribute to significant depletion of ozone levels. Officials from the United Nations have said that the ozone loss was “unprecedented, but not entirely unexpected.”
As of late March, the thinning ozone has begun to move away from the pole and headed towards Greenland and Scandinavia. Because sunlight further contributes to ozone loss, Johnson has recommended inhabitants of northern regions take precautions when outside, including wearing sunscreen and sunglasses.
Photo credit: NASA