The ozone hole that arose over the Arctic last winter became the "deepest" in the entire history of observations (over 20 years) and approached in scale to the Antarctic ozone hole, according to an article published in the journal Nature
The sharp drop in stratospheric ozone concentration, the "ozone hole", was first discovered in the 1980s over Antarctica. According to modern concepts, the destruction of ozone (triatomic molecules of oxygen O3) is associated with the effect of substances from the group of chlorofluorocarbons (CFCs), the most famous of which is the group of freons.
Under the influence of sunlight and stratospheric cold, these substances form aggressive chlorine compounds that destroy the ozone layer - the shield that protects life on Earth from the harmful hard ultraviolet radiation. In 1987, the Montreal Protocol was adopted, which forbids the production of CFCs, but their natural extinction will take several decades.
In the winter and spring of 2010-2011, for the first time, a process was observed in the Arctic that could be called the formation of an ozone hole. In early April, the World Meteorological Organization announced that the amount of ozone in the atmosphere in the Arctic region this winter has dropped by a record 40%.
A team of scientists led by Gloria Manney from NASA's Jet Propulsion Laboratory analyzed in detail the formation of the ozone hole and came to the conclusion that this event was unprecedented in scale, and in the event that the winter in the Arctic is slightly more severe, the concentration ozone will be even sharper.
“This is the first time this is happening in our north. The decrease in the amount of ozone in the Arctic has always been much less pronounced than in Antarctica. In 1994-1995, there was a 30% drop, but this had never happened before. Now the drop was 40%, this is already comparable to Antarctica, there is an ozone hole of 50% -60%. The order is already the same,”one of the authors of the study, Valery Dorokhov, a senior researcher at the Central Aerological Observatory of Roshydromet, told RIA Novosti.
The ozone hole in the polar regions occurs when, due to low temperatures in the stratosphere (below 78 degrees below zero), water vapor and nitric acid form the so-called polar stratospheric clouds. These clouds and other cold aerosols give long-lived chlorine compounds, particularly chlorofluorocarbons, the ability to convert to highly reactive compounds such as chlorine oxide, which kill ozone.
In the winter of 2010-2011, a circumpolar vortex, a strip of strong stratospheric air currents around the polar zone, which did not allow warm air to reach the pole, persisted for an unusually long time in the Arctic. As a result, by the beginning of spring, the ozone concentration dropped sharply.
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“This period, when the air is cold, usually lasts 2-2.5 months. And this time it dragged on for four months - until April, although it usually ends in March,”said Dorokhov.
Scientists note that temperatures below the 78-degree threshold in the Arctic have stayed between 15 and 23 degrees for over 100 days. At the same time, the fall in the amount of ozone below the level of 250 Dobson units in the spring was observed within 27 days, and below 230 - during the week.
“In this regard, the reduction in the amount of ozone in the Arctic has for the first time reached a level at which one can speak of an Arctic ozone hole,” the article says. Its authors note that the area bounded by the circumpolar vortex in the Arctic is much smaller than in Antarctica, but it is more mobile.
"More severe ozone depletion in the Arctic could increase biological risks from greater exposure to ultraviolet radiation, especially if the vortex zone moves towards the more densely populated mid-latitudes, as happened in April 2011," the scientists write.
The increase in the strength of ultraviolet radiation can lead, in particular, to an increase in the number of cases of cataracts, Dorokhov notes.
The authors of the study say that at the moment there are no methods how to predict the recurrence of such cases of sharp decreases in the amount of ozone. For their development, it is necessary to collect more accurate data on the state of the winter stratosphere.
“Therefore, we must be ready, must constantly monitor. Observations of ozone in Russia have been going on since the 1960s, but these are measurements of total content. The vertical distribution is measured by only one station in Salekhard. Now, together with scientists from St. Petersburg, we plan to make one more point at the hydrometeorological observatory in Tiksi,”Dorokhov said.