July 31st US Global Change Seminar: "What's Happening To Stratospheric Ozone Over The Arctic, And Why?"
tsocci at usgcrp.gov
Wed Jul 26 14:21:29 EDT 2000
U.S. Global Change Research Program Seminar Series
What's Happening To Stratospheric Ozone Over The Arctic, And Why?
Is Arctic stratospheric ozone presently undergoing depletion? Is this an
unusual, unique or unanticipated phenomenon? Are the underlying causes of
this phenomenon the same as those that are responsible for the Antarctic
ozone hole? If not, how are they different? Does climate change (i.e.,
global warming) play a role? Do these factors alter the projected timing
of recovery of the stratospheric ozone layer to 1979 levels? If so, what
is the new projection for recovery of the stratospheric ozone layer in the
Monday, July 31, 2000, 3:15-4:45 PM
Dirksen Senate Office Building, Room 628
Dr. Michael Kurylo, Manager of the Upper Atmosphere Research Program,
National Aeronautics and Space Administration (NASA), Washington, DC
Dr. Paul A. Newman, NASA Goddard Space Flight Center Greenbelt, MD
Over the last decade, some very low ozone levels have been observed
over the Arctic during the late winter and early spring. These low
values have hightened concerns that human activity may be seriously
impacting the Arctic stratosphere and raise question regarding the nature
and timing of ozone recovery over the next few decades.
In 1985, large ozone losses were observed over the Antarctic region.
NASA satellite observations showed that this ozone loss covered an
extensive region, coining its name, the Antarctic ozone hole. The
Antarctic ozone hole was subsequently shown to result from chlorine and
bromine destruction of stratospheric ozone. The stratospheric chlorine and
bromine levels primarily come from human produced chemicals such as
chlorofluorocarbons (CFCs) and halons whose concentrations had been
increasing throughout the 1970s and 80s. Naturally occurring, extremely
cold temperatures over Antarctica cause the formation of very tenuous
clouds (polar stratospheric clouds or PSCs). Certain chlorine and bromine
compounds are then converted from benign forms into ozone destructive forms
when they come into contact with the surfaces of the cloud particles.
Hence, the massive ozone loss over Antarctica results from the unique
meteorological conditions and the high levels of human produced chlorine
and bromine. Because production of CFCs and halons has been curtailed, the
Antarctic ozone hole is expected to return to 1979 levels late in this
The Arctic stratosphere is considerably different than the Antarctic
stratosphere. First, natural ozone levels in the Arctic spring are much
higher than in the Antarctic spring. Second, Arctic spring
stratospheric temperatures are much warmer than those in the Antarctic
stratosphere. Because of the warmer Arctic stratospheric temperatures,
polar stratospheric clouds are much less common than over Antarctica.
However, measurements of chlorine compounds in the Arctic stratosphere
measured in 1989 and 1991-92 showed that chlorine levels could lead to
massive ozone losses if the stratospheric cold winter conditions persisted
into the mid-to-late spring.
Observations and modeling over the last decade have shown that
conditions for severe ozone loss are directly related to the severity
and persistence of the Arctic winter. The persistence of cold
temperatures leads to the formation of extensive polar stratospheric
clouds which in turn activate chlorine and lead to large ozone losses.
Since high levels of chlorine compounds will be common over the next 50-70
years, the predicition of ozone levels is dependent on the
detailed physics of the formation of these polar stratospheric clouds
and on the prediction of future temperatures in the stratosphere.
Current projections suggest that climate change may lead to large
cooling of the stratosphere, leading to more extensive PSC formation
and greater ozone loss. Thus, ozone layer recovery may not track the
slow decline of industrial halogen compounds in the atmosphere.
During the 1999-2000 winter, the NASA sponsored SAGE III Ozone Loss and
Validation Experiment (SOLVE) and the European Union sponsored Third
European Stratospheric Experiment on Ozone (THESEO 2000) obtained
measurements of ozone and other atmospheric gases and particles using
satellites and aircrafts, large, small and long duration balloons, and
ground-based instruments throughout the Arctic. Ozone losses of over 60%
were observed in the Arctic stratosphere near 18 km altitude during one of
the coldest stratospheric winters on record. These losses were a direct
result of chlorine and bromine species activated on the surfaces of polar
Dr. Newman has been with NASA since1990. He is now a senior level
atmospheric physicist at NASA's Goddard Space Flight Center in the
Atmospheric Chemistry and Dynamics Branch. Prior to his joining NASA, he
served as a National Research Council fellow, and served for a time with
the Applied Research Corporation and the Universities Space Research
Associates. Dr. Newman is principally involved in the analysis of
stratospheric meteorological and trace gas observations. He was a
co-project scientist of the SAGE III Ozone Loss and Validation Experiment,
and is actively engaged in a number of other experiments related to
understanding and modeling processes governing the transport of chemical
species throughout the atmosphere, and monitoring, measuring and modeling
tropospheric and stratospheric ozone in various regions of the globe.
Public education is a principal goal of NASA and as such, Dr. Newman helped
put together a web-based document on stratospheric ozone issues.
Dr. Newman is a member of the American Meteorological Society, Middle
Atmosphere Committee (1998-present), and has served on the American
Meteorological Society's Committee on Polar Meteorology and Oceanography
(1989-1992). Dr. Newman is also a member of the American Geophysical Union
and is an associate editor of the Journal of Geophysical Research.
Dr. Newmsn's awards include: the L. H. Brown Pre-Doctoral Fellowship; a
National Research Council Postdoctoral Fellowship; several NASA group
Achievement Awards going back to 1990; several NASA Goddard Space Flight
Center (GSFC) Outstanding performance awards from1991-1999; the Naval
Research Laboratory's Alan Berman Research Publication Award, the American
Geophysical Union Excellence in Reviewing Award for Journal of Geophysical
Research; and a GSFC Special Act award for his work on SOLVE (2000).
Dr. Newman is a Seattle native who graduated from Seattle University in1978
with a B.S. in Physics and a minor in mathematics. He completed his
doctorate in physics at Iowa State University in 1984.
The Next Seminar is tentatively scheduled for September 20, 2000
Tentative Topic: Land Use and Land Cover Changes and the Movement and
Storage of Carbon: Results of the New IPCC (Intergovernmental Panel on
Climate Change) Report on Land Use, Land-Use Change, and Forestry
For more information please contact:
Anthony D. Socci, Ph.D., U.S. Global Change Research Program Office, 400
Virginia Ave. SW, Suite 750, Washington, DC 20024; Telephone: (202)
314-2235; Fax: (202) 488-8681 E-Mail: TSOCCI at USGCRP.GOV.
Additional information on the U.S. Global Change Research Program (USGCRP)
and this Seminar Series is available on the USGCRP Home Page at:
http://www.usgcrp.gov. A complete archive of seminar summaries can also be
found at this site under the link: "Second Monday Seminars."
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