A NASA instrument has detected an Antarctic ozone "hole" (what
scientists call an "ozone depletion area") that is three times larger
than the entire land mass of the United Statesthe largest such area
The "hole" expanded to a record size of approximately 11 million
square miles (28.3 million square kilometers) on Sept. 3, 2000. The
previous record was approximately 10.5 million square miles (27.2
million square km) on Sept. 19, 1998.
The ozone hole's size currently has stabilized, but the low levels in
its interior continue to fall. The lowest readings in the ozone hole are
typically observed in late September or early October each year.
"These observations reinforce concerns about the frailty of Earth's
ozone layer. Although production of ozone-destroying gases has been
curtailed under international agreements, concentrations of the gases in
the stratosphere are only now reaching their peak. Due to their long
persistence in the atmosphere, it will be many decades before the ozone
hole is no longer an annual occurrence," said Dr. Michael J. Kurylo,
manager of the Upper Atmosphere Research Program, NASA Headquarters,
Ozone molecules, made up of three atoms of oxygen, comprise a thin
layer of the atmosphere that absorbs harmful ultraviolet radiation from
the Sun. Most atmospheric ozone is found between approximately six
miles (9.5 km) and 18 miles (29 km) above the Earth's surface.
Scientists continuing to investigate this enormous hole are somewhat
surprised by its size. The reasons behind the dimensions involve both
early-spring conditions, and an extremely intense Antarctic vortex. The
Antarctic vortex is an upper-altitude stratospheric air current that
sweeps around the Antarctic continent, confining the Antarctic ozone
"Variations in the size of the ozone hole and of ozone depletion
accompanying it from one year to the next are not unexpected," said Dr.
Jack Kaye, Office of Earth Sciences Research Director, NASA
Headquarters. "At this point we can only wait to see how the ozone hole
will evolve in the coming few months and see how the year's hole
compares in all respects to those of previous years."
"Discoveries like these demonstrate the value of our long-term
commitment to providing key observations to the scientific community,"
said Dr. Ghassem Asrar, Associate Administrator for NASA's Office of
Earth Sciences at Headquarters. "We will soon launch QuickTOMS and
Aura, two spacecraft that will continue to gather these important data."
The measurements released today were obtained using the Total Ozone
Mapping Spectrometer (TOMS) instrument aboard NASA's Earth Probe
(TOMS-EP) satellite. NASA instruments have been measuring Antarctic
ozone levels since the early 1970s. Since the discovery of the ozone
"hole" in 1985, TOMS has been a key instrument for monitoring ozone
levels over the Earth.
TOMS ozone data and more pictures are available at:
TOMS-EP and other ozone-measurement programs are important parts of a
global environmental effort of NASA's Earth Science enterprise, a
long-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.