Ozone Layer Loss In The Arctic May Be A Record (But Don't Panic)
    By News Staff | March 14th 2011 12:37 PM | 6 comments | Print | E-mail | Track Comments
    Low temperatures in the Arctic 'ozone layer' have recently initiated massive ozone depletion, which means the Arctic could experience a record loss of this trace gas that protects the Earth's surface against ultraviolet radiation from the sun. The result has been found by a measurement network of over 30 ozone sounding stations spread all over the Arctic and Subarctic.

    In the long term the ozone layer will recover thanks to extensive environmental policy measures enacted decades ago for its protection. This winter's likely record-breaking ozone loss does not alter this expectation.

    Our atmosphere has five layers; the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere.   The so-called ozone layer is in the stratosphere at an altitude of 20-30 kilometers. As you might infer, the ozone layer has high levels of ozone, which is due to interaction between oxygen molecules (composed of two oxygen atoms) and ultraviolet light.   Ozone is able to absorb harmful ultraviolet radiation, wavelengths between 290-320 nanometers.   

    Ozone is lost in three ways:  Volcanic eruptions in a small sense (5%), other natural occurrences (20%), but the bulk of the ozone breakdown happens when anthropogenic chlorofluorocarbons (CFCs) are turned into aggressive, ozone destroying substances - an effect made worse during exposure to extremely cold conditions. 

    For several years climate scientists have pointed to a connection between ozone loss and climate change, and particularly to the fact that in the Arctic stratosphere where the ozone layer is, the coldest winters seem to have been getting colder and are leading to larger ozone losses, though "the complicated details of the interactions between the ozone layer and climate change haven't been completely understood yet and are the subject of current research projects," explains Alfred Wegener Institute climate researcher Markus Rex. "The current winter is a continuation of this development, which may indeed be connected to global warming."

    The Dobson Unit - how ozone is measured

    A Dobson Unit is a measurement of how thick the ozone layer would be if it were compressed into a single layer at zero degrees Celsius with one unit of atmospheric pressure acting on it (standard temperature and pressure - STP).   One Dobson Unit (DU) is defined as .01 mm thickness at standard temperature and pressure.  This graphic from the University of Michigan shows a column of air over Labrador, Canada. Since the ozone layer over this area would form a 3 mm thick slab, the measurement of the ozone over Labrador is 300 DU.

    dobosn unit how the ozone layer is measured

    As stated before, this loss is not a reason to panic, though primarily because environmental changes were made before the situation was critical.

    "By virtue of the long-term effect of the Montreal Protocol, significant ozone destruction will no longer occur during the second half of this century," explains Rex. The Montreal Protocol is an international treaty adopted under the UN umbrella in 1987 to protect the ozone layer and for all practical purposes bans the production of ozone-depleting chlorofluorocarbons (CFCs) worldwide today.

    CFCs released during prior decades however, will not vanish from the atmosphere until many decades from now. Until that time the fate of the Arctic ozone layer essentially depends on the temperature in the stratosphere at an altitude of around 20 km and thus will linked to any changes in earth's climate.


    I had heard of another hypothesis: Ironically another pollutant comes to ozone's partial rescue at higher temperatures by interfering with chlorine free radical. That pollutant is nitrogen dioxide. But at lower temperatures the NO2 is trapped in polar stratospheric clouds, and Cl is free to form more chlorine monoxide by reacting with ozone.
    Enrico: you may have a valid point.  There's a lot of runoff going into the Arctic.  At least some smallish part of that must be from lands where artificial fertilizers - a source of NO2 - are being used.
    I'm not sure about NO2 from agricultural sources. They are certainly a source of N2O. But there are various nitrogen oxides of the NOX variety in volcanic emissions.
    Oops!  My bad!  NO2 is the clean stuff from Big power - N2O is the dirty stuff from Big agro.

    Or something like that.

    P.S.  I like to tease just to see who is awake around here. ;-)
    Don't worry...I'm surprised I was awake enough to catch it....I should take a little break from Science 2.0 again...I have a mountain of lab reports and tests to correct, and at the midcentury mark in age, I no longer have the fastest red pen in the west.
    For those asking why is this hole forming? What makes this year different?
    or why do they keep mentioning the cold air and what does it have to do with the ozone?

    The hole exists, because the ozone is being forced out of the area by the cold air.
    Ozone O3 is a 3 piece oxygen molecule created by a reaction of sunlight and oxygen in the atmosphere. It is always being created anywhere the sun hits oxygen in the air, and destroyed by sunlight hitting the Ozone (O3).
    In the antarctic the ice is so thick that a polar vortex always forms during their long night of winter ( a month or so with no sunlight at all.) during that time the cold air pushes all the warm air out and forms almost a wall of cold.
    Because the Ozone is formed by sunlight it is warm when created, so is also pushed out. It's dark during the arctic winter so no Ozone is created there during that time so a hole forms.
    Now normally because there is no land mass at the North pole, and very little inside the arctic circle, there is not normally enough ice mass to set up a polar vortex there, but this year it was unusually cold. A vortex formed and then so did an Ozone hole.
    In both the arctic and the antarctic the ozone hole collapses once the sun rises again and heats the air enough to break the vortex.
    Ozone is created by the sun, and again the sun has the answer for the reduction and the stratospheric cooling, it has nothing to do with CFC's or Global warming for that matter
    "March 2, 2011: In 2008-2009, sunspots almost completely disappeared for two years. Solar activity dropped to hundred-year lows; Earth's upper atmosphere cooled and collapsed; the sun’s magnetic field weakened, allowing cosmic rays to penetrate the Solar System in record numbers. It was a big event, and solar physicists openly wondered, where have all the sunspots gone?"

    There is a risk though for maybe a few weeks that this cold air mass before it breaks up does not have the ozone levels in it to guard against UV radiation in these very northern cities and towns and they could be at risk to skin cancer from the elevated UV.