Brian Dunbar Headquarters, Washington, D.C. October 6, 1994 (Phone: 202/358-1547) Allen Kenitzer Goddard Space Flight Center, Greenbelt, Md. (Phone: 301/286-8955) RELEASE: 94-167 ANTARCTIC OZONE HOLE LEVELS SAME AS LAST YEAR'S RECORD LOWS A NASA instrument aboard a Russian satellite has detected a hole in the ozone layer over Antarctica with a surface area equal to the size of the North American continent. The Antarctic ozone hole levels for 1994 are nearly as large and as deep as the record lows from October 1993, according to preliminary data obtained by scientists at NASA's Goddard Space Flight Center, Greenbelt, Md. These record low levels were recorded by NASA's Total Ozone Mapping Spectrometer (TOMS) instrument aboard the Russian Meteor-3 satellite. Similar low ozone amounts over the Antarctic continent also have been observed by balloon-borne instruments flown from the South Pole, ground-based Dobson spectrometers and an instrument on the U.S. NOAA-9 satellite. "The pattern of ozone loss is much the same as last year," said Dr. Jay R. Herman, research scientist, Laboratory for Atmospheres, at Goddard. "The minimum ozone amounts measured by Meteor-3 TOMS have dropped below 100 Dobson units near the center of the Antarctic continent, with values just above 100 Dobson units measured over a wide area." The size of the ozone hole region has nearly leveled off in 1992, 1993 and 1994, at about nine million square miles (24 million square kilometers). During these years, the ozone depletion area has nearly filled the polar-vortex wind region that places an upper bound on the possible size of the ozone hole. A Dobson unit is the physical thickness of the ozone layer if it were brought to the Earth's surface (300 Dobson units equals three millimeters or 1/10th of an inch). -more- -2- Ozone, a molecule made up of three atoms of oxygen, forms a thin layer of the atmosphere which absorbs harmful ultraviolet radiation from the Sun. The term "ozone hole" is used to describe a large area of intense ozone depletion that occurs over Antarctica during late August through early October and typically breaks up in late November. The largest hole ever observed was on September 27, 1992, when the hole had an extent of 9.4 million square-miles (24.4 million square-kilometers). Since the mid-1980s, scientists have observed the region covered by low total ozone beginning to grow in early August. This region has typically reached its maximum extent in late September and its greatest depth in early October. Scientists have determined that chlorine products from human activities, such as electronics and refrigeration uses, are a primary cause for the ozone hole formation. Since the discovery of the ozone hole in 1985, TOMS has been the key instrument for monitoring ozone levels throughout the southern hemisphere. The TOMS aboard NASA's Nimbus-7 satellite measured Antarctic ozone levels from November 1978 to May 1993. During its lifetime on Nimbus-7, TOMS made ozone a household word through pictures of the Antarctic ozone hole. TOMS data also provided part of the scientific underpinning for the Montreal Protocol, under which many of the world's developing nations have agreed to phase out the use of ozone- depleting chemicals. The NASA TOMS instrument on the Russian Meteor-3 satellite has been measuring ozone since its launch in 1991, and since May 1993 it has been the primary source of NASA's ozone data. NASA plans to fly three more TOMS instruments on a U.S. Earth Probe satellite, scheduled for launch in 1995, a Japanese Advanced Earth Observing Satellite in 1996 and on another Russian satellite at the end of the decade. TOMS is part of NASA's Mission to Planet Earth, which is studying how the global environment is changing. Using the unique perspective from space, NASA is observing, monitoring and assessing large-scale environmental processes. TOMS and other satellite data, complemented by aircraft and ground data, will allow scientists to better understand natural environmental changes and to distinguish natural changes from human induced changes. TOMS ozone data and pictures are available to anyone with a computer connection to the Internet at http//hypatia.gsfc.nasa.gov/nasa_hottopics.html. The TOMS instruments are managed by the Goddard Space Flight Center for NASA's Office of Mission to Planet Earth, Washington, D.C. -more- -3- NOTE TO EDITORS: A TOMS data image is available to editors, upon request, to illustrate this story. The image shows the ozone levels over a region near the South Pole for October 2, 1994. Interested media should call the Goddard Space Flight Center at (301) 286-8995, or fax their request on letterhead to the Headquarters Broadcast and Imaging Branch, (202) 358-4333. -end- NASA press releases and other information are available automatically by sending an Internet electronic mail message to domo@hq.nasa.gov. In the body of the message (not the subject line) users should type the words "subscribe press-release" (no quotes). The system will reply with a confirmation via E-mail of each subscription. A second automatic message will include additional information on the service.