Extremes in Antarctic ozone holes not matched in the Arctic

Ozone hole during Oct. 7, 2008, as measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) atmospheric sensor onboard ESA's Envisat. 

Credit: KNMI /ESA

Since the discovery of the Antarctic ozone hole, scientists, policymakers, and the public have wondered whether we might someday see a similarly extreme depletion of ozone over the Arctic.

But a new MIT study finds some cause for optimism: Ozone levels in the Arctic haven't yet sunk to the extreme lows seen in Antarctica, in part because international efforts to limit ozone-depleting chemicals have been successful.

"While there is certainly some depletion of Arctic ozone, the extremes of Antarctica so far are very different from what we find in the Arctic, even in the coldest years," says Susan Solomon, the Ellen Swallow Richards Professor of Atmospheric Chemistry and Climate Science at MIT, and lead author of a paper published this week in the Proceedings of the National Academy of Sciences.

Frigid temperatures can spur ozone loss because they create prime conditions for the formation of polar stratospheric clouds.

When sunlight hits these clouds, it sparks a reaction between chlorine from chlorofluorocarbons (CFCs), human-made chemicals once used for refrigerants, foam blowing, and other applications, ultimately destroying ozone.

"A success story of science and policy"
After the ozone-attacking properties of CFCs were discovered in the 1980s, countries across the world agreed to phase out their use as part of the 1987 Montreal Protocol treaty.

While CFCs are no longer legally in use, those gasses emitted in previous years, remain active in the atmosphere.

As a result, atmospheric concentrations have peaked and are now slowly declining, but it will be several decades before CFCs are totally eliminated from the environment; meaning there is still some risk of ozone depletion caused by CFCs.

"It's really a success story of science and policy, where the right things were done just in time to avoid broader environmental damage," says Solomon, who made some of the first measurements in Antarctica that pointed toward CFCs as the primary cause of the ozone hole.

To obtain their findings, the researchers used balloon and satellite data from the heart of the ozone layer over both polar regions.

They found that Arctic ozone levels did drop significantly during an extended period of unusual cold in the spring of 2011.

While this dip did depress ozone levels, the decrease was nowhere near as drastic as the nearly complete loss of ozone in the heart of the layer seen in many years in Antarctica.

The MIT team's work also helps to show chemical reasons for the differences, demonstrating that ozone loss in Antarctica is closely associated with reduced levels of nitric acid in air that is colder than that in the Arctic.

"We'll continue to have cold years with extreme Antarctic ozone holes for a long time to come," Solomon says.

"We can't be sure that there will never be extreme Arctic ozone losses in an unusually cold future year, but so far, so good, and that's good news."

More information: "Fundamental differences between Arctic and Antarctic ozone depletion," by Susan Solomon, Jessica Haskins, Diane J. Ivy, and Flora Min. PNAS, 2014. www.pnas.org/cgi/doi/10.1073/pnas.1319307111

NASA WASP: Planetary scientists gain new observation platform

Scientists used the Wallops Arc Second Pointer (WASP) to precisely point the HyperSpectral Imager for Climate Science during a balloon mission in September. 

Shown here after it landed, the imager collected radiance data for nearly half of its eight-and-a-half hour flight. 

Credit: NASA

Scientists who study Earth, the sun and stars have long used high-altitude scientific balloons to carry their telescopes far into the stratosphere for a better view of their targets.

Not so much for planetary scientists. That's because they needed a highly stable, off-the-shelf-type system that could accurately point their instruments and then track planetary targets as they moved in the solar system. That device now exists.

NASA's Wallops Flight Facility in Wallops Island, Va., has designed a new pointing system, the Wallops Arc Second Pointer (WASP), that can point balloon-borne scientific instruments at targets with sub arc-second accuracy and stability.

A planetary scientist—interested in finding less-expensive platforms for observing Jupiter and other extraterrestrial bodies—now plans to test drive the device later this year.

David Stuchlik

"Arc-second pointing is unbelievably precise," said David Stuchlik, the WASP project manager.

"Some compare it to the ability to find and track an object that is the diameter of a dime from two miles away."

WASP is designed to be a highly flexible, standardized system capable of supporting many science payloads, Stuchlik added.

Its development frees scientists, who in the past had to develop their own pointing systems, to instead focus on instrument development.

Given the technology's potential, the WASP team has received NASA Science Mission Directorate funding to further enhance the new capability as a standard support system.

First tested in 2011 and then again in 2012, the most recent test flight occurred from Fort Sumner, N.M., in September 2013.

During that flight, a 30-story balloon lifted an engineering test unit of the HyperSpectral Imager for Climate Science (HySICS) to an altitude of nearly 122,000 feet, far above the majority of Earth's atmosphere.

From this vantage point, WASP precisely pointed HySICS so that it could measure Earth, the sun and the moon.

Developed by Greg Kopp of the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP), the imager collected radiance data for nearly half of its eight-and-a-half hour flight, demonstrating improved techniques for future space-based radiance tests.

Kopp now is preparing his imager for another balloon flight this September.