| September 25, 2003
2003 Ozone 'Hole' Approaches, But Falls Short Of Record
This year's Antarctic ozone hole is the second largest ever observed,
according to scientists from NASA, the National Oceanic and Atmospheric
Administration (NOAA), and the Naval Research Laboratory.
The Antarctic ozone hole is defined as thinning of the ozone layer over
the continent to levels significantly below pre-1979 levels. Ozone blocks
harmful ultraviolet "B" rays. Loss of stratospheric ozone has been linked
to skin cancer in humans and other adverse biological effects on plants
and animals.
The size of this year's hole reached 10.9 million square miles on September
11, 2003. It was slightly larger than the North American continent, but
smaller than the largest hole ever recorded, on September 10, 2000, when
it covered 11.5 million square miles. Last year the ozone hole was smaller,
covering 8.1 million square miles.
NASA's Earth Probe Total Ozone Mapping Spectrometer and the NOAA-16
Solar Backscatter Ultraviolet instrument provided ozone measurements
from space. These data were coupled with data collected by NOAA's Climate
Monitoring and Diagnostics Laboratory (CMDL) from balloon-borne instruments,
which measure the ozone hole's vertical structure.
NASA's own scientist Paul Newman said, "While chlorine and bromine chemicals
cause the ozone hole, extremely cold temperatures, especially near the
edge of Antarctica, are also key factors in ozone loss."
Given the leveling or slowly declining atmospheric abundance of ozone-destroying
gases, the year-to-year changes in the size and depth of the ozone hole
are dominated by the year-to-year variations in temperature in this part
of the atmosphere. The fact this year's ozone loss is much greater than
last year's reflects the very different meteorological conditions between
these two years.
NASA scientist Rich McPeters said ozone observations showed the total
amount of ozone from surface to space was 106 Dobson Units (DU) on September
14, 2003, the minimum value reached this year. "Dobson units" measure
the "thickness" of protective ozone in the stratosphere. They range from
100 DU to 500 DU, which translate to about 1 millimeter (1/25 inch) to
5 millimeters (1/5 inch) of ozone in a layer.
Bryan Johnson of CMDL said the ozone depletion region, from 7-to-14
miles above the Earth, has large losses, similar to losses seen in the
1990s. If the stratospheric temperature remains cold over the pole, then
we should see complete ozone loss in the 9-13 mile layer, with total
column ozone reaching 100 DU by early October.
The Montreal Protocol and its amendments banned chlorine-containing
chlorofluorocarbons (CFCs) and bromine-containing halons in 1995, because
of their destructive effect on the ozone. However, CFCs and halons are
extremely long-lived and still linger at high concentrations in the atmosphere.
However, the atmospheric abundances of ozone destroying chemicals are
beginning to decline. As a result, the Antarctic ozone hole should disappear
in about 50 years.
NASA's Earth Science Enterprise is dedicated to understanding the Earth
as an integrated system and applying Earth System Science to improve
prediction of climate, weather, and natural hazards using the unique
vantage point of space. For more information and images on the Internet,
visit:
http://www.gsfc.nasa.gov/topstory/2003/0925ozonehole.html
NOAA is dedicated to enhancing economic security and national safety
through the prediction and research of weather and climate-related events
and providing environmental stewardship of our nation's coastal and marine
resources. To learn more about NOAA, visit:
http://www.noaa.gov
###
Contacts:
Elvia H. Thompson
Headquarters, Washington
(Phone: 202/358-1696)
Carmeyia Gillis
NOAA Climate Prediction Center, Camp Springs, Md.
(Phone: 301/763-8000, ext. 7163)
Dick Thompson
Naval Research Laboratory, Washington
(Phone: 202/767-1936) |
|
2003 Antarctic Ozone 'Hole'
By mid-September 2003, the ozone thinning already extended over 28.2
million square kilometers (10.9 million square miles). The maximum area
in 2000 reached 29.2 million square kilometers, the largest on record.
Since winter temperatures dipped lower than usual, driving the chemical
reactions that deplete ozone, this year's 'hole' (dark blue) was very
large. The thinnest point so far this year is 106 Dobson Units (a layer
about 1.06 millimeters at sea-level pressure), 40% as thick as normal
levels. This series shows the daily extent of the ozone 'hole,' regions.
Data come from NASA's Total Ozone Mapping Spectrometer (TOMS) on the
Earth Probe satellite, from Aug. 1-Sept. 23, 2003.
High-Resolution
Image
 
Calm Cool Skies Spell Losses
This year, colder temperatures and calmer winds allowed chemical reactions
that break down ozone to occur at about the same rates as the past few
years. However, last year's unusually moderate Antarctic temperatures
and highly variable upper atmospheric winds kept the ozone 'hole' relatively
small, about 40% smaller in area than the record sizes seen in 2000,
2001, and this year. In 2002, the 'hole' also split into two parts for
the first time since 1979, also due to unusual weather patterns. These
comparisons pit the near-record size of this year's 'hole' against a)
the small area of last year's hole and b) the split shape from last year.
Data from TOMS-EP.
Nearing the Road to Recovery
Last year's unusual reduction in ozone losses proved just that — unusual.
The ozone hole grew larger throughout the late 1980's and early 1990's,
as shown in this time series of maximum areas from 1979 to 2002 (excluding
1995). This year the hole reached nearly the same size as 2000 and 2001,
larger than the North American continent. While the manufacture and use
of chlorofluorocarbons and halons (CFCs) that contribute to yearly ozone
destruction have decreased, the chemicals will linger in the upper atmosphere
for decades before the ozone layer will consistently recover.
  
Arctic Losses Closer to Home
While the Antarctic regularly experiences ozone losses, warmer temperatures
in the Arctic prevent such massive losses from occurring as often near
the North Pole. However, when large Arctic ozone losses occur, the depletion
can threaten populated areas with harmful doses of ultraviolet rays.
Here we show the winters of 1997, 2000, and 2003, particularly severe
losses stretching over populated areas such as Northern Europe. Data
from TOMS-EP.
New Satellite to See Ozone
NASA's soon-to-be-launched Aura satellite will see ozone in both the
upper and lower atmosphere for the first time. Current missions examine
ozone in an isolated part of the atmosphere, but Aura will track ozone
and other gas transport between the lower and upper atmosphere. This
information is extremely important to understanding the long-term health
of the upper atmosphere. Aura's new sensors will give scientists a more
complete three-dimensional picture of atmospheric ozone distribution. |
