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Oct. 21, 2019 NASA2019

Ozone Hole is the Smallest on Record Since Its Discovery

Abnormal weather patterns in the upper atmosphere over Antarctica dramatically limited ozone depletion in September and October, resulting in the smallest ozone hole observed since 1982, NASA and NOAA scientists reported today.

The annual ozone hole reached its peak extent of 6.3 million square miles (16. 4 million square kilometers) on Sept. 8, and then shrank to less than 3.9 million square miles (10 million square kilometers) for the remainder of September and October, according to NASA and NOAA satellite measurements. During years with normal weather conditions, the ozone hole typically grows to a maximum area of about 8 million square miles in late September or early October.

“It’s great news for ozone in the Southern Hemisphere,” said Paul Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Greenbelt, Maryland. “But it’s important to recognize that what we’re seeing this year is due to warmer stratospheric temperatures. It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery.”

Ozone is a highly reactive molecule comprised of three oxygen atoms that occurs naturally in small amounts. Roughly seven to 25 miles above Earth’s surface, in a layer of the atmosphere called the stratosphere, the ozone layer is a sunscreen, shielding the planet from potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and also damage plants.

The Antarctic ozone hole forms during the Southern Hemisphere’s late winter as the returning Sun’s rays start ozone-depleting reactions. These reactions involve chemically active forms of chlorine and bromine derived from man-made compounds. The chemistry that leads to their formation involves chemical reactions that occur on the surfaces of cloud particles that form in cold stratospheric layers, leading ultimately to runaway reactions that destroy ozone molecules. In warmer temperatures fewer polar stratospheric clouds form and they don’t persist as long, limiting the ozone-depletion process.

NASA and NOAA monitor the ozone hole via complementary instrumental methods.

Satellites, including NASA’s Aura satellite, the NASA-NOAA Suomi National Polar-orbiting Partnership satellite and NOAA’s Joint Polar Satellite System NOAA-20 satellite, measure ozone from space. The Aura satellite’s Microwave Limb Sounder also estimates levels of ozone-destroying chlorine in the stratosphere.

At the South Pole, NOAA staff launch weather balloons carrying ozone-measuring “sondes” which directly sample ozone levels vertically through the atmosphere. Most years, at least some levels of the stratosphere, the region of the upper atmosphere where the largest amounts of ozone are normally found, are found to be completely devoid of ozone.

“This year, ozonesonde measurements at the South Pole did not show any portions of the atmosphere where ozone was completely depleted,” said atmospheric scientist Bryan Johnson at NOAA’s Earth System Research Laboratory in Boulder, Colorado.

Uncommon but not unprecedented

This is the third time in the last 40 years that weather systems have caused warm temperatures that limit ozone depletion, said Susan Strahan, an atmospheric scientist with Universities Space Research Association, who works at NASA Goddard. Similar weather patterns in the Antarctic stratosphere in September 1988 and 2002 also produced atypically small ozone holes, she said.

“It’s a rare event that we’re still trying to understand,” said Strahan. “If the warming hadn’t happened, we’d likely be looking at a much more typical ozone hole.”

There is no identified connection between the occurrence of these unique patterns and changes in climate.

The weather systems that disrupted the 2019 ozone hole are typically modest in September, but this year they were unusually strong, dramatically warming the Antarctic’s stratosphere during the pivotal time for ozone destruction. At an altitude of about 12 miles (20 kilometers), temperatures during September were 29 degrees F (16˚C) warmer than average, the warmest in the 40-year historical record for September by a wide margin. In addition, these weather systems also weakened the Antarctic polar vortex, knocking it off its normal center over the South Pole and reducing the strong September jet stream around Antarctica from a mean speed of 161 miles per hour to a speed of 67 miles per hour. This slowing vortex rotation allowed air to sink in the lower stratosphere where ozone depletion occurs, where it had two impacts.

First, the sinking warmed the Antarctic lower stratosphere, minimizing the formation and persistence of the polar stratospheric clouds that are a main ingredient in the ozone-destroying process. Second, the strong weather systems brought ozone-rich air from higher latitudes elsewhere in the Southern Hemisphere to the area above the Antarctic ozone hole. These two effects led to much higher than normal ozone levels over Antarctica compared to ozone hole conditions usually present since the mid 1980s.

As of October 16, the ozone hole above Antarctica remained small but stable and is expected to gradually dissipate in the coming weeks.

Antarctic ozone slowly decreased in the 1970s, with large seasonal ozone deficits appearing in the early 1980s. Researchers at the British Antarctic Survey discovered the ozone hole in 1985, and NASA’s satellite estimates of total column ozone from the Total Ozone Mapping Spectrometer confirmed the 1985 event, revealing the ozone hole’s continental scale.

Thirty-two years ago, the international community signed the Montreal Protocol on Substances that Deplete the Ozone Layer. This agreement regulated the consumption and production of ozone-depleting compounds. Atmospheric levels of man-made ozone depleting substances increased up to the year 2000. Since then, they have slowly declined but remain high enough to produce significant ozone loss. The ozone hole over Antarctica is expected to gradually become less severe as chlorofluorocarbons— banned chlorine-containing synthetic compounds that were once frequently used as coolants—continue to decline. Scientists expect the Antarctic ozone to recover back to the 1980 level around 2070.

 

To learn more about NOAA and NASA efforts to monitor the ozone and ozone-depleting gases, visit:

https://ozonewatch.gsfc.nasa.gov/

https://www.cpc.ncep.noaa.gov/products/stratosphere/polar/polar.shtml

https://www.esrl.noaa.gov/gmd/dv/spo_oz/

By: Ellen Gray

NASA's Earth Science News Team

By:  Theo Stein

National Oceanic and Atmospheric Administration

 

Last Updated: Oct. 22, 2019Editor: Sara Blumberg



NASA Ozone Watch

Five questions about 2019's record-small ozone hole

Author: 
NOAA
October 21, 2019

How did the 2019 ozone hole compare to previous years?

In 2019, the hole that developed in the ozone layer over Antarctica was the smallest on record since 1982, according to the NASA/NOAA press release. In an average spring, the hole expands throughout September and early October to a maximum extent of about 8 million square miles (21 million square kilometers), an area larger than the United States and Canada combined. In 2019, the hole reached 6.3 million square miles (16.4 million square kilometers) on September 8, but then shrank to less than 3.9 million square miles (10 million square kilometers) for the remainder of September and the first half of October.

The ozone hole is a seasonal thin spot that develops in the ozone layer, which, over the South Pole, resides at altitudes from 9-13 miles (14-21 kilometers). It’s observed with both satellites and with weather balloons that NOAA scientists launch at the South Pole. The satellites measure the ozone hole’s area, and the weather balloons measure ozone concentrations as they drift up through a column of the atmosphere. Locations where the total ozone concentration falls below 220 Dobson units are considered part of the ozone hole.

In most years since the hole was discovered, weather balloons rising through the atmospheric column have passed through regions where ozone is completely absent from the middle stratosphere. In 2019, however, they found no segments of the South Pole profile that were completely devoid of ozone.

This graph shows ozone concentrations in a column of the stratosphere (12–22 kilometers) above the South Pole from the start of the observational record in 1986 through 2019.  Red areas are parts of the atmospheric column with high levels of ozone; white and pale gray show areas where little to no ozone was detected during annual weather balloon launches. Similar to 1988 and 2012, the 2019 balloon profiles did not find any segments of the ozone layer where ozone was completely depleted. NOAA Climate.gov image, based on original provided by Bryan Johnson, NOAA Earth System Research Lab.  

Why was the ozone hole so small this year? 

An uncommon weather event—a sudden stratospheric warming—disrupted the circulation in the polar stratosphere in early September, just as the ozone hole was beginning to form. Warmth in the stratosphere reduces the formation of polar stratospheric clouds, which are a critical link in the chain of events that lead to the ozone hole.

The rapid warm-up came from a breakdown of the Antarctic polar vortex, a slowly-spinning pool of stratospheric air trapped by a ring of fierce westerly winds—the polar night jet—that emerges in the upper stratosphere during winter at the South Pole. In an average September, this jet blows at an average speed of 161 miles per hour, equivalent to an F3 category tornado or a Category 5 hurricane. Plunged into darkness and cut off from warmer latitudes, air in the vortex can reach temperatures colder than -90 degrees Celsius.

Every once in a while, however, the polar night jet is disrupted by strong planetary waves in the atmosphere below. In September 2019, one of these waves—unusually strong for the time of year—jostled the polar stratosphere, slowing the jet to just 67 miles hour and knocking the polar vortex off center. When the jet slows, the air inside the vortex sinks, and as it sinks, it warms dramatically due to compression. Beginning in late August 2019, temperatures at 10 millibars rose by more than 70 degrees F (40 degrees Celsius) in just 10 days. September 2019 temperatures at an altitude of about 12 miles (20 kilometers) were 29 degrees F (16˚C) warmer than average, the warmest in the historical record by a wide margin.

An unusually strong disruption of the Southern Hemisphere polar vortex in late winter 2019 caused temperatures in the polar stratosphere to skyrocket. Each column in this image shows the departure from average temperatures for the region from 60-90 degrees South latitude at altitudes between the surface and 50 kilometers. In late August, temperatures in the stratosphere spiked (deep red area at image right). NOAA Climate.gov image, adapted from original provided by Craig Long, NOAA Climate Prediction Center. 

The breakdown of the polar vortex helped the ozone hole in two ways. The early season warmth minimized further condensation and persistence of polar stratospheric clouds, which can only form at temperatures below -78 degrees C. Because these clouds enable the chemistry that produces ozone-destroying substances, fewer clouds meant less ozone destruction.

The breakdown of the polar vortex also allowed more ozone-rich air from lower latitudes of the Southern Hemisphere to mix into the polar stratosphere. Normally, the polar night jet is an invisible barrier around the South Pole stratosphere, preventing air from other parts of the Southern Hemisphere from mixing in to the vortex. When the polar vortex weakened in early September, an influx of air from lower latitudes was able to partially patch the hole that had begun to form. The lingering warmth prevented it from reforming.

Was the unusual warmth that diminished the 2019 ozone hole the result of global warming? 

There is no known connection between sudden stratospheric warming events and human-caused global warming. These events are very rare in the Southern Hemisphere: this is only the third time in 40 years that one has been observed in the Antarctic stratosphere. (They happen more often in the Arctic, where the polar vortex is generally weaker and polar temperatures are warmer, which is why the Arctic doesn’t usually have an ozone hole.) Conditions similar to this September’s occurred in September 1988 and 2002. Those years also produced small ozone holes. 

It’s important to be clear that the South Pole’s sudden stratospheric warming was a weather event, not a long-term warming trend. In fact, the same greenhouse gases that are causing Earth’s surface and lower atmosphere to warm are simultaneously causing the stratosphere to cool. This cooling trend may even slightly delay the full healing of the ozone layer.

Does this year's small ozone hole mean recovery is going faster than we thought? 

No, this year’s small ozone hole was simply the result of an isolated weather event, not part of a trend. Thanks to the international treaty banning the production and use of CFCs (short for chlorofluorocarbons), levels of these compounds have been declining since about 2000. But because CFCs are so long-lived, concentrations remain high enough to cause significant ozone loss each spring. With continued declines in CFCs, experts project the ozone layer will recover to its 1980 conditions around 2070.

Last year, NOAA scientists reported on some unexpected violations of the Montreal Protocol's ban on CFCs. Why didn't these rogue emissions make this year's ozone hole worse?

In May 2018, NOAA scientists reported that starting in 2012, the global concentration of CFC-11 had stopped declining. At a July meeting of the parties to the Montreal Protocol, members of the Protocol’s Scientific Assessment Panel further reported that most likely explanation for the interrupted trend was new, unreported emissions. While new production of CFCs is not compatible with long-term recovery of the ozone hole, the new emissions will not have an immediate impact on the ozone hole. That’s because it takes several years for CFCs for new CFCs to reach the ozone layer. Atmospheric scientists say that despite the rogue emissions, this year’s ozone hole would likely have been similar to other recent years if not for the unusual weather conditions.

https://www.climate.gov/news-features/understanding-climate/five-questions-about-2019s-record-small-ozone-hole

 

Antarctic Situation at 2019 November 25British Antarctic Survey

Antarctic ozone today:  The 2019 ozone hole is over and ozone amounts are high across most of the continent.  Ozone amounts range from around 300 DU to 380 DU.  The temperature of the ozone layer is well above the-78°C Polar Stratospheric Cloud (PSC) formation threshold and continues to rise.   It is now generally a little above average values and is highest over Antarctica and declines towards the equator.  The polar vortex has dissipated roughly a week earlier than seen in the last decade.

The 2019 ozone hole:  The 2019 polar vortex began to form in May and had reached some 20 million square kilometres in area near the base of the ozone layer by early July; this was smaller than over the last decade.   At the time of the solstice, the growing polar vortex was unusually offset towards the Indian Ocean and centred over East Antarctica.  It returned to being more pole centred and by early August was some 28 million square kilometres in area.  After the solstice it was near the smallest over the last decade and was generally offset towards the Atlantic.  It reached its maximum size in late August, unusually early and only during this period was it close to the average size for the decade.  Overall the stratosphere was quite disturbed during the winter, with strong wave activity with a period of around a month, and this gave rise to the smaller than usual vortex and ozone hole.   The vortex dissipated in late November, roughly a week earlier than in any year over the previous decade.  Temperatures in the ozone layer were below the  -78°C Polar Stratospheric Cloud (PSC) formation threshold from late May until the equinox.  A sudden spring warming of the stratosphere began in early September.   Such an early pulse of warming in the stratosphere was not uncommon in the years prior to the formation of an ozone hole in the 1980s, but it has been rarer in the last 30 years.  More stable conditions returned in October and during the month the temperature rose more slowly and by the end of the month was close to the normal with the spring warming having subsided.  The area with potential PSCs reached a peak of some 26 million square kilometres in area at times from mid July to August and then declined rapidly.  Satellite observations show that the ozone hole began to grow from mid-August and reached a peak of around 11 million square kilometres in area in early September.  It then shrank to 3 million square kilometres by the time of the equinox as a result of the early warming.  More stable conditions returned in late September and the hole re-grew to a peak size of some 8 million square kilometres in area in mid October, still smaller than seen over the last decade.   The final decline came in early November, slightly later than the ozone hole of 2017. 

 

Antarctic Situation at 2019 October 4British Antarctic Survey

Antarctic ozone today:  An annual stratospheric warming commenced unusually early this year and temperatures are rising through much of the ozone layer.  The area above Antarctica with Polar Stratospheric Clouds (PSCs) has dropped to near zero, the smallest at this time of year for decades.  The polar vortex has begun to shrink and is now 23 million square kilometres in area near the base of the ozone layer; this is smaller than it has been in the last decade.  It is shrinking more rapidly higher in the ozone layer.  The vortex is offset from the Pole towards the Atlantic.  Lowest ozone amounts, around 190 DU, are over Dronning Maud Land.  Ozone amounts are much higher around Antarctica over the southern ocean with amounts near 450 DU in places.  The ozone hole is currently some 7 million square kilometres in area, down from a peak of around 11 million square kilometres in area in early September and smaller than ever seen in the last decade.   Overall the stratosphere has been much less stable than usual, which is giving rise to the small size of the vortex.  More stable conditions have returned and the ozone hole is expected to remain stable over the coming 10 days, remaining offset from the pole towards the Atlantic.

Antarctic Situation at 2019 September 27 British Antarctic Survey

Antarctic ozone today:  The annual stratospheric warming has commenced unusually early this year and temperatures are rising through much of the ozone layer.  The area above Antarctica with Polar Stratospheric Clouds (PSCs) has dropped to only 1 million square kilometres, the smallest at this time of year for decades.  The polar vortex has begun to shrink and is now 24 million square kilometres in area near the base of the ozone layer; this is smaller than it has been in the last decade.  It is shrinking more rapidly higher in the ozone layer.  The vortex is offset from the Pole towards the Atlantic.  Lowest ozone amounts, around 190 DU, are over West Antarctica.  Ozone amounts are much higher around Antarctica over the southern ocean with amounts over 440 DU in places.  The ozone hole is currently some 5 million square kilometres in area, down from a peak of around 11 million square kilometres in area in early September and smaller than ever seen in the last decade.   Overall the stratosphere is much less stable than usual, which is giving rise to the small size of the vortex.  More stable conditions are returning and ozone depletion is expected to slightly increase over the coming 10 days, with the hole remaining offset from the pole.


Antarctic Situation at 2019 August 30 British Antarctic Survey

Antarctic ozone today:  The 2019 polar vortex began to form in May and has reached some 32 million square kilometres in area near the base of the ozone layer; this is smaller than it has been in the past two years.  It is larger higher up.  The growing polar vortex is offset from the Pole towards the Antarctic Peninsula.  Ozone depletion is increasing, with lowest amounts below 200 DU over the base of the Antarctic Peninsula.  Ozone amounts are building over the southern ocean  and here amounts are higher, over 450 DU in places.  Satellite observations show that the 2019 ozone hole began to grow from mid-August and is currently some 5 million square kilometres in area, fractionally larger than in the past two years.   Temperatures in the ozone layer are nearing the long winter minimum and are below the  -78°C Polar Stratospheric Cloud (PSC) formation threshold through much of the ozone layer, though the highest part has in places warmed above the threshold.  The area potentially with clouds now covers 21 million square kilometres, close to the average for the date over the last decade.  It is down from a peak of 26 million square kilometres in mid July.   Overall the stratosphere is much less stable than usual, which is giving rise to the small size of the vortex.  Stratospheric temperatures are highest over mid latitudes and decline towards the equator and the pole. They are generally close to the average throughout the ozone layer.  Ozone depletion is expected to increase over the Antarctic Peninsula and Weddell Sea over the coming 10 days.

Antarctic Situation at 2019 August 12 British Antarctic Survey

Antarctic ozone today:  The 2019 polar vortex began to form in May and has reached some 29 million square kilometres in area near the base of the ozone layer; this is around the smallest it has been at this date over the last decade.  It is larger higher up.  The growing polar vortex is offset from the Pole towards the Antarctic Peninsula.  Ozone depletion is increasing, with lowest amounts below 200 DU over the base of the Antarctic Peninsula.  Ozone amounts are building over the southern ocean  and here amounts are higher, over 400 DU in places.  Temperatures in the ozone layer are nearing the long winter minimum and are below the  -78°C Polar Stratospheric Cloud (PSC) formation threshold through much of the ozone layer, though the highest part has in places warmed above the threshold.  The area potentially with clouds now covers 24 million square kilometres, close to the average for the date over the last decade.  It is down from a peak of 26 million square kilometres in mid July.   Overall the stratosphere is much less stable than usual, which is giving rise to the small size of the vortex.  Stratospheric temperatures are highest over mid latitudes and decline towards the equator and the pole. They are generally close to the average throughout the ozone layer.  Ozone depletion is expected to increase over West Antarctica and the Antarctic Peninsula over the coming 10 days.



Antarctic Situation at 2019 July 26 British Antarctic Survey

Antarctic ozone today:  The 2019 polar vortex began to form in May and has reached some 25 million square kilometres in area near the base of the ozone layer, and is larger higher up; this is smaller than the average over the last decade.  The growing polar vortex is roughly centred on the pole.  Lowest ozone values, around 220 DU, are over the base of the Antarctic Peninsula.  Ozone amounts are building over the southern ocean  and here amounts are higher, over 400 DU in places.  Temperatures in the ozone layer are nearing the long winter minimum and have reached the  -78°C Polar Stratospheric Cloud (PSC) formation threshold through much of the ozone layer.  The area potentially with clouds now covers 24 million square kilometres, close to the mean over the last decade.  Stratospheric temperatures are highest over mid latitudes and decline towards the equator and the pole. They are generally a little below average throughout the ozone layer. 




NASA Ozone Watch

Antarctic Situation at 2019 July 5 British Antarctic Survey

Antarctic ozone today:  The 2019 polar vortex began to form in May and has reached some 20 million square kilometres in area near the base of the ozone layer, and is larger higher up; this is smaller than over the last decade.  The temperature throughout the ozone layer is falling overall.  The growing polar vortex has moved back towards the pole, having been unusually offset towards the Indian Ocean and centred over East Antarctica at the time of the solstice.  Lowest ozone values, around 210 DU, are over the base of the Antarctic Peninsula and Rothera experienced its first day of ozone hole values on July 2.  Ozone amounts are building over the southern ocean  and here amounts are higher, up to 370 DU in places.  Temperatures in the ozone layer are nearing the long winter minimum and have reached the  -78°C Polar Stratospheric Cloud (PSC) formation threshold through much of the ozone layer.  The area potentially with clouds now covers 22 million square kilometres, close to the mean over the last decade.  Stratospheric temperatures are highest over mid latitudes and decline towards the equator and the pole.  In the lower stratosphere they are not far from the normal, though are below the normal in the upper part of the ozone layer. 


Environment Canada



Ozone Hole July 2019

Ozone Hole August 2019

 Ozone Hole September 2019

Ozone Hole October 2019