United Nations (UN) and U.S. scientists said that the Antarctic ozone hole has grown bigger. In fact, 2015 has witnessed a 28.2 million square kilometer-hole, which is about the size of Russia and Canada combined. The reason for such confounding environmental news is said to be due to the cold temperatures over the Antarctic.
Paul Krummel, of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) said that the actual driver of the ozone hole year by year are meteorological conditions. In 2015, the Antarctic stratosphere temperature has been extremely cold. Normally, warm air begins to escape in that area around October but this has not occurred yet.
Scientists said that every year, the size of the hole changes as it emerges. Krummel said the ozone stratosphere over Antarctica has undergone exhaustion every spring over the last 35 years due to two vital factors.
The rise in the so-called ozone-depleting chemicals up in the atmosphere, together with distinctive cold conditions during spring and winter in the Antarctic are the key factors that give out a one-of-a-kind catalytic ozone destruction vessel. This enables the swift disappearance of the ozone through higher amounts of chlorofluorocarbons. Chlorofluorocarbons are the ozone-depleting agents that reach the atmosphere due to human activity.
World Meteorological Organization (WMO) releases its Antarctic Ozone Bulletin nearly every two to three weeks from August to November. The information found in this bulletin are provided by the Global Atmosphere Watch group of WMO which facilitates the ozone-monitoring centers in the southern hemisphere.
When winter comes in the southern hemisphere, the atmosphere over the Antarctic is decreased from exchanges with mid-latitude air via the polar vortex, which is a massive pocket of very cold air that is situated over the polar region. Primary damage in ozone transpires in this said area.
The extremely cold temperatures of the polar vortex may lead to what is known as polar stratospheric clouds (PSCs).
As spring arrives in the polar region, the integration of returning sunlight and the PSCs results in the emission of chlorine radicals that highly react and eventually destroy the ozone.
In 2015, ozone depletion occurred late due to the extended stay of the polar vortex in the polar night from July and most of August. When the sun came back to the area during the latter part of August, ozone exhaustion picked up rapidly. As the polar vortex stayed put, the temperatures in the stratosphere became low.
The 2008 and 2015 maximum ozone holes are similar. However, in 2015, the polar vortex remained cold and firm, and there has been very minimal movement of ozone-rich air from the middle latitudes.
"Ozonesonde data from several stations confirm that ozone depletion has stopped, but the data also show that ozone remains depleted in the 12-20 km altitude range," wrote Geir Braathen in a WMO technical report.
WMO together with various scientific groups will use ground-based tools to continuously monitor the developments during the rest of the season.
Photo: Fee Plumley | Flickr