Antarctic ozone hole similar to last year

The Antarctic ozone hole, which forms annually in the August to October period, reached its peak size on September 11, stretching to 9.3 million square miles (24.1 million square kilometers), roughly the same size as last year’s peak of 9.3 million square miles (24 million square kilometers) on September 16, 2013. This is an area similar in size to North America.

Ozone hole
This image, using NOAA satellite data, shows the ozone hole (areas below 220 Dobson units) in shades of red. (Credit: NOAA Visualization Lab; http://www.nnvl.noaa.gov/MediaDetail2.php?MediaID=1636&MediaTypeID=1)

In comparison, the largest ozone hole area recorded to date on a single day was on September 9, 2000, at 11.5 million square miles (29.9 million square kilometers). The ozone layer helps shield life on Earth from potentially harmful ultraviolet (UV) radiation that can cause skin cancer, damage plants and phytoplankton—the top of the oceanic food chain.

“The good news is that our measurements show less thinning of the ozone over the South Pole during the past three years,” said Bryan Johnson, a researcher with NOAA’s Earth System Research Laboratory in Boulder, Colorado. “However, the rate at which ozone thins during the month of September has remained about the same for the past two decades. A decrease in this rate will be an important sign of recovery.”

South Pole balloon-borne ozonesonde observations measured a minimum amount of 120 Dobson Units of ozone this year on September 29. Ozonesonde measurements of 250 Dobson Units in August are common just before the rapid destruction of ozone in September.  NOAA releases about 50-60 ozonesonde balloons per year since 1986 to measure the ozone layer at the South Pole.  Over the last 50 years satellite and ground-based records over Antarctica show ozone column amounts ranging from 100 to 400 Dobson units, which translates to about 1 millimeter (1/25 inch) to 4 millimeters (1/6 inch) of ozone in a layer if all of the ozone were brought down to the surface.

The Antarctic ozone hole began making a yearly appearance in the early 1980s, grew in size through the 1980s and has been consistently large since 1990, with annual variability attributed to stratospheric meteorological conditions over Antarctica. The hole is caused by chlorine released by manmade chemicals called chlorofluorocarbons or CFCs that were extensively used as aerosol sprays and in refrigerators.

Ozonesonde release
NOAA Corps LTJG Joseph Phillips releases an ozonesonde that's attached to a helium balloon. The instrument will rise 18 miles into the atmosphere to measure the thickness of ozone. (Credit: Chet Waggoner, NOAA)

These chlorine compounds lead to ozone depletion in certain upper atmospheric conditions. These conditions are at their peak over Antarctica as the dark cold winter gives way to the Antarctic spring in September. Just before the sun rises over Antarctica, extremely cold temperatures in the stratosphere allow for polar stratospheric clouds to form, a rare event in the earth’s atmosphere, but a regular occurrence in the winter over Antarctica. Chemical reactions on the cloud particles convert stable chlorine compounds into unstable or reactive forms. The sun light triggers reactive chlorine and ozone chemistry that depletes ozone in a large volume over Antarctica.

Scientists first made the connection that CFCs were depleting the earth’s protective layer in 1974. In 1987, 46 nations, including the U.S., signed the Montreal Protocol, a landmark agreement to phase out production of ozone-depleting chemicals. The slow recovery of this ozone layer is one of the great international efforts to restore the planet from manmade damage.

The 2014 level of ozone depleting substances over Antarctica has declined about 9 percent below the 2000 recorded maximum. But CFCs can remain in the atmosphere for more than 50 years. The ozone layer above Antarctica likely will not return to its 1980 state until about 2070, said Paul Newman, chief scientist for atmospheres at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Climate change may also affect the rate of ozone recovery by cooling the stratosphere, which can slow Antarctic ozone recovery.

“Year-to-year weather variability significantly impacts Antarctica ozone because warmer stratospheric temperatures can reduce ozone depletion,” said Paul A. Newman, chief scientist for atmospheres at NASA's Goddard Space Flight Center in Greenbelt, Maryland. “The ozone hole area is smaller than what we saw in the late-1990s and early 2000s, and we know that chorine levels are decreasing. However, we are still uncertain about whether a long-term Antarctic stratospheric temperature warming might be reducing this ozone depletion.”

Under the mandate of the Clean Air Act, NOAA and NASA scientists keep a close eye on the ozone layer’s health with satellite data, ground-based measurements and instruments sent up through the ozone layer via balloons. Together, these instruments provide a big picture of the thickness and area extent of the ozone hole. NOAA measures the thickness of the ozone using ground-based instruments and by sending balloons with measurement devices up 18 miles into the atmosphere from NOAA’s Antarctic station.

NOAA and NASA also use data taken by the Ozone Mapping Profiler Suite (OMPS) instrument on board the Suomi-National Polar-Orbiting Partnership satellite to monitor the earth’s ozone layer. This instrument replaced the NOAA Solar Backscatter UltraViolet/2 ozone profiler and NASA Total Ozone Mapping Spectrometer.  NOAA’s Climate Prediction Center has been monitoring the Earth’s ozone layer for over 30 years, analyzing ozone concentration at various altitudes in the ozone layer as well as the total column amount of ozone. These measurements provide a three dimensional perspective of the ozone layer. This provides the means to monitor the ozone layer’s health and to make sure it is on the road to recovery.

Source: NOAA

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2014 Antarctic ozone hole holds steady

This image shows ozone concentrations above Antarctica on Sept. 11, 2014. Credit: NASA

The single-day maximum area was similar to that in 2013, which reached 24.0 million square kilometers (9.3 million square miles). The largest single-day ozone hole ever recorded by satellite was 29.9 million square kilometers (11.5 million square miles) on Sept. 9, 2000. Overall, the 2014 ozone hole is smaller than the large holes of the 1998-2006 period, and is comparable to 2010, 2012, and 2013.

With the increased atmospheric chlorine levels present since the 1980s, the Antarctic ozone hole forms and expands during the Southern Hemisphere spring (August and September). The ozone layer helps shield life on Earth from potentially harmful ultraviolet radiation that can cause skin cancer and damage plants.

The Montreal Protocol agreement beginning in 1987 regulated ozone depleting substances, such as chlorine-containing chlorofluorocarbons and bromine-containing halons. The 2014 level of these substances over Antarctica has declined about 9 percent below the record maximum in 2000.

"Year-to-year weather variability significantly impacts Antarctica ozone because warmer stratospheric temperatures can reduce ozone depletion," said Paul A. Newman, chief scientist for atmospheres at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The ozone hole area is smaller than what we saw in the late-1990s and early 2000s, and we know that chlorine levels are decreasing. However, we are still uncertain about whether a long-term Antarctic stratospheric temperature warming might be reducing this ozone depletion."

Scientists are working to determine if the ozone hole trend over the last decade is a result of temperature increases or chorine declines. An increase of stratospheric temperature over Antarctica would decrease the ozone hole's area. Satellite and ground-based measurements show that chlorine levels are declining, but stratospheric temperature analyses in that region are less reliable for determining long-term trends.

Scientists also found that the minimum thickness of ozone layer this year was recorded at 114 Dobson units on Sept. 30, compared to 250-350 Dobson units during the 1960s. Over the last 50 years satellite and ground-based records over Antarctica show ozone column amounts ranging from 100 to 400 Dobson units, which translates to about 1 millimeter (1/25 inch) to 5 millimeters (1/6 inch) of ozone in a layer if all of the ozone were brought down to the surface.

The ozone data come from the Dutch-Finnish Ozone Monitoring Instrument on NASA's Aura satellite and the Ozone Monitoring and Profiler Suite instrument on the NASA-NOAA Suomi National Polar-orbiting Partnership satellite. NOAA measurements at South Pole station monitor the ozone layer above that location by means of Dobson spectrophotometer and regular ozone-sonde balloon launches that record the thickness of the ozone layer and its vertical distribution. Chlorine amounts are estimated using NOAA and NASA ground measurements and observations from the Microwave Limb Sounder aboard NASA's Aura satellite.

NASA and NOAA are mandated under the Clean Air Act to monitor ozone-depleting gases and stratospheric depletion of ozone. Scientists from NASA and NOAA have been monitoring the ozone layer and the concentrations of ozone-depleting substances and their breakdown products from the ground and with a variety of instruments on satellites and balloons since the 1970s. These observations allow us to provide a continuous long-term record to track the long-term and year-to-year evolution of ozone amounts.

Source:  NASA/Goddard Space Flight Center

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Expect higher grass pollen, allergen exposure in coming century

A study provides the first evidence that pollen production is significantly stimulated by elevated carbon dioxide in a grass species as a result of climate change, which may have significant impact on human health. Credit: UMass Amherst

Results of a new study by scientists at the University of Massachusetts Amherst strongly suggest that there will be notable increases in grass pollen production and allergen exposure up to 202 percent in the next 100 years, leading to a significant, worldwide impact on human health due to predicted rises in carbon dioxide (CO2) and ozone (O3) due to climate change.

While CO2 stimulates reproduction and growth in plants, ozone has a negative impact on plant growth, the authors point out. In this study in Timothy grass, researchers led by environmental health scientist Christine Rogers of the UMass Amherst School of Public Health and Health Sciences (SPHHS) determined the interactive effects of CO2 and ozone at projected higher levels on pollen production and concentrations of a Timothy grass pollen protein that is a major human allergen. Findings are reported in the current issue of PLOS ONE.

Rogers and plant science colleagues at UMass Amherst, with postdoctoral researcher and first author Jennifer Albertine, write, "The implications of increasing CO2 for human health are clear. Stimulation of grass pollen production by elevated CO2 will increase airborne concentrations and increase exposure and suffering in grass pollen-allergic individuals."

Rogers notes that, "This is the first evidence that pollen production is significantly stimulated by elevated carbon dioxide in a grass species and has worldwide implications due to the ubiquitous presence of grasses in all biomes and high prevalence of grass pollen allergy. These results are similar to our other studies performed in other highly allergenic taxa such as ragweed but with more extreme outcomes and wider impacts."

For these experiments, the researchers exposed grass plants in specially designed continuously stirred tank reactor chambers that allow researchers to expose plants to different atmospheric gas concentrations. They established four experimental atmospheric treatments:

• control, current atmosphere (30 ppb O3 and 400 ppm CO2)
• elevated O3, current CO2 (80 ppb O3, 400 ppm CO2)
• current O3, elevated CO2 (30 ppb O3, 800 ppm CO2)
• elevated O3, elevated CO2 (80 ppb O3, 800ppm CO2)

At the appropriate plant development stage, Albertine and colleagues bagged flowers, captured and measured pollen amounts and extracted the allergen protein Phl p 5 from pollen samples for measurement by enzyme-linked immunosorbent assay (ELISA).

They found that elevated CO2 of 800 ppm, increased pollen production per flower by 53 percent while the different ozone levels had no effect on the amount of pollen produced. There was also a trend of increased number of plants flowering in response to elevated CO2 further increasing pollen production up to 200 percent. While elevated ozone did decrease the Phl p 5 allergen content in pollen, "the strong CO2-stimulation of pollen production suggests increased exposure to Timothy grass allergen overall," even if O3 projections are realized, the authors note.

They add that the health implications of increased ozone are "more complex" because higher levels of this greenhouse gas irritate mucous membranes and worsen the allergic airway response. Projected ozone increases "would likely elicit negative respiratory health effects independent of any health effects as a result of increased pollen by elevated CO2."

Source:  University of Massachusetts at Amherst

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