October 3, 2011
Scientists Detect First-Ever Arctic Ozone Hole
A team of international researchers, led by NASA scientists, has discovered an unprecedented loss of protective ozone in the atmosphere above the Arctic this year, according to various media reports published on Sunday.
That phenomenon, according to an AFP article, has led to the formation of an ozone hole five times the size of the state of California. It marks the first time that ozone loss in the Arctic region has matched ozone loss above Antarctica, both they and Postmedia News are reporting.
According to LiveScience Senior Writer Wynne Parry, the researchers discussed their finding in this Sunday's edition of the journal Nature, writing, ""For the first time, sufficient loss occurred to reasonably be described as an Arctic ozone hole."
Parry reports that more than 80% of the ozone present at altitudes of 11 to 12 miles in January had been "chemically destroyed" less than three months later.
In an October 2 press release, the American space agency said that scientists from 19 different institutions spread across 9 different countries, including the U.S., Canada, Germany, Russia, and Japan, analyzed trace gas and cloud measurements from NASA spacecraft. They also used balloons to measure ozone, while studying meteorological and atmospheric models as well.
"Day-to-day temperatures in the 2010-11 Arctic winter did not reach lower values than in previous cold Arctic winters," lead author Gloria Manney, representing NASA's Jet Propulsion and the New Mexico Institute of Mining and Technology, said in a statement.
"The difference from previous winters is that temperatures were low enough to produce ozone-destroying forms of chlorine for a much longer time. This implies that if winter Arctic stratospheric temperatures drop just slightly in the future, for example as a result of climate change, then severe Arctic ozone loss may occur more frequently," she added.
The 2011 Arctic ozone loss occurred over an area considerably smaller than that of the Antarctic ozone holes. This is because the Arctic polar vortex, a persistent large-scale cyclone within which the ozone loss takes place, was about 40 percent smaller than a typical Antarctic vortex.
While smaller and shorter-lived than its Antarctic counterpart, the Arctic polar vortex is more mobile, often moving over densely populated northern regions. Decreases in overhead ozone lead to increases in surface ultraviolet radiation, which are known to have adverse effects on humans and other life forms.
NASA also reports that, while the total amount of ozone measured in the Arctic this spring was "much more than twice" the average amounts of the Antarctic region during the same time, the amount of ozone destroyed was "comparable" to the amount of some prior Antarctic ozone holes, mainly because ozone levels are typically much higher in the Arctic.
"The ozone destruction began in January, then accelerated in late February and March, so that ozone values in the polar vortex region were much lower than usual from early March through late April, after which the polar vortex dissipated," Manney told the AFP.
"Especially low total column ozone values (below 250 Dobson Units) were observed for about 27 days in March and early April," she added. "The maximum area with values below 250 Dobson Units was about two million square kilometers (772,000 square miles), roughly five times the area of Germany or California."
"Winter in the Arctic stratosphere is highly variable -- some are warm, some are cold," Michelle Santee, also of the Jet Propulsion Laboratory, told BBC News Environmental Correspondent Richard Black on Sunday. "But over the last few decades, the winters that are cold have been getting colder“¦ So given that trend and the high variability, we'd anticipate that we'll have other cold ones, and if that happens while chlorine levels are high, we'd anticipate that we'd have severe ozone loss."
Santee added that the region experienced unusually steady cold temperatures from December through April. "That had never happened before in the Arctic in the instrumental record," she told Black, adding that it would take "years of detailed study" to determine exactly why that happened.
Image Caption: Left: Ozone in Earth's stratosphere at an altitude of approximately 12 miles (20 kilometers) in mid-March 2011, near the peak of the 2011 Arctic ozone loss. Red colors represent high levels of ozone, while purple and grey colors (over the north polar region) represent very small ozone amounts. Right: chlorine monoxide — the primary agent of chemical ozone destruction in the cold polar lower stratosphere — for the same day and altitude. Light blue and green colors represent small amounts of chlorine monoxide, while dark blue and black colors represent very large chlorine monoxide amounts. The white line marks the area within which the chemical ozone destruction took place. Image credit: NASA/JPL-Caltech
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