A NASA instrument has detected an Antarctic ozone "hole" (whatscientists call an "ozone depletion area") that is three times largerthan the entire land mass of the United States—the largest such areaever observed.
The "hole" expanded to a record size of approximately 11 millionsquare miles (28.3 million square kilometers) on Sept. 3, 2000. Theprevious record was approximately 10.5 million square miles (27.2million square km) on Sept. 19, 1998.
The ozone hole's size currently has stabilized, but the low levels inits interior continue to fall. The lowest readings in the ozone hole aretypically observed in late September or early October each year.
"These observations reinforce concerns about the frailty of Earth'sozone layer. Although production of ozone-destroying gases has beencurtailed under international agreements, concentrations of the gases inthe stratosphere are only now reaching their peak. Due to their longpersistence in the atmosphere, it will be many decades before the ozonehole is no longer an annual occurrence," said Dr. Michael J. Kurylo,manager of the Upper Atmosphere Research Program, NASA Headquarters,Washington, DC.
Ozone molecules, made up of three atoms of oxygen, comprise a thinlayer of the atmosphere that absorbs harmful ultraviolet radiation fromthe Sun. Most atmospheric ozone is found between approximately sixmiles (9.5 km) and 18 miles (29 km) above the Earth's surface.
Scientists continuing to investigate this enormous hole are somewhatsurprised by its size. The reasons behind the dimensions involve bothearly-spring conditions, and an extremely intense Antarctic vortex. TheAntarctic vortex is an upper-altitude stratospheric air current thatsweeps around the Antarctic continent, confining the Antarctic ozonehole.
"Variations in the size of the ozone hole and of ozone depletionaccompanying it from one year to the next are not unexpected," said Dr.Jack Kaye, Office of Earth Sciences Research Director, NASAHeadquarters. "At this point we can only wait to see how the ozone holewill evolve in the coming few months and see how the year's holecompares in all respects to those of previous years."
"Discoveries like these demonstrate the value of our long-termcommitment to providing key observations to the scientific community,"said Dr. Ghassem Asrar, Associate Administrator for NASA's Office ofEarth Sciences at Headquarters. "We will soon launch QuickTOMS andAura, two spacecraft that will continue to gather these important data."
The measurements released today were obtained using the Total OzoneMapping Spectrometer (TOMS) instrument aboard NASA's Earth Probe(TOMS-EP) satellite. NASA instruments have been measuring Antarcticozone levels since the early 1970s. Since the discovery of the ozone"hole" in 1985, TOMS has been a key instrument for monitoring ozonelevels over the Earth.
TOMS ozone data and more pictures are available at:
TOMS-EP and other ozone-measurement programs are important parts of aglobal environmental effort of NASA's Earth Science enterprise, along-term research program designed to study Earth's land, oceans,atmosphere, ice and life as a total integrated system.
For more information about ozone and ozone loss, visit: Ozone in the Stratosphere.
References & Resources
Image courtesy the TOMS science team & and the Scientific Visualization Studio, NASA GSFC
