Why is the gap in the ozon layer the worst above Antartica,
given that the highest emission of CFK's happens in the Northern Hemisphere?
Asked by: Micha Duchateau
Well now this is a really great question. I often wondered about this same fact. Before
I explain this I would like to first explain tides to you. If I asked you what makes the
tides, I might expect you to tell me the moon, but could you explain why there are 2 high
tides and 2 low tides a day even though the moon only circles once a day?
If we look at the situation where we have a lunar eclipse, there is a high tide on the
side of the earth that the sun and moon are, and there is another high tide on the
opposite side of the earth than the sun and the moon. The gravitational pull of the sun
and moon cause the high tide on the side of the earth that they are on but what causes
that other high tide? The second high tide is caused by the centrifugal force cause by
the earth orbiting the sun. These 2 high tides stay right where they are, and as the
earth spins, we see the tides 'go around the earth'. The fact that extra water is
pulled to these 2 places makes low tides everywhere else (including the north and south
So why did I tell you about the tides? You see the atmosphere does the same thing that
the water does. This means at the north and south pole, the atmosphere is thinner than
anywhere else on earth, because the air is pulled away from there. Ozone is in the same
percentage all around the earth (because gasses diffuse % evenly) so it is natural that
there is less at the poles. This is why the 'gap' in the ozone is thinner at Antarctica
than in the populated region of the northern hemisphere.
Answered by: Paul Flaherty Jr, B.S., Mechanical Engineer, Bosch, Charleston SC.
Ozone is an unstable molecular form of oxygen.
Each molecule of ozone consists of three, rather
than two, atoms of oxygen.
Ozone can be created in any number of ways, but
the relatively abundant ozone found in the
upper atmosphere is formed when normal oxygen
there is bombarded by ultra-violet radiation
from the Sun which breaks the molecules apart,
and, some people suspect, aid in their combining
into the three-atom ozone molecule. Because there
is much more ultra-violet radiation high in our
atmosphere than there is down near the Earth's
surface, there is much more ozone up there than
there is down here. In essence the ozone
molecules are the 'wounded veterans' of a
never-ending war between UV rays and oxygen. This
stratospheric 'warfare' between ultra-violet rays
and oxygen deflects and renders harmless much of
the ultra-violet radiation coming in at us from
the Sun. That is why we worry about the so-called
'ozone layer.' It isn't an actual layer of gas,
but the constant interaction of UV rays and oxygen
way up there protects us from excess UV rays down
During the southern hemisphere's winter months
the Sun does not shine in Antarctica for many
weeks at a time. During that time the Sun does
not deliver ultra-violet radiation to the upper
atmosphere over the South Pole. So ozone
production there ceases during this period of
time. Also during the South Polar winter a
characteristic whirlpool of winds forms there
which prevents the air down there from doing much
mixing with the rest of the Earth's atmosphere.
The same type of vortex sometimes forms at the
North Pole during its winter months, but it is
much weaker. Most people knowledgeable on the
subject think the difference is due to the fact
that Antarctica is a continent with elevated
features while the North Polar region is largely
flat, frozen ocean. For whatever reasons, the
northern vortex is much less isolational than the
southern vortex. There is much more exchange
movement of air across the North Pole in winter
than there is over the South Pole.
So in the southern winter months ozone production
over the Antarctic region dwindles and the ozone
over the region becomes depleted. This so-called
'ozone hole' -- which is actually nothing more
than an area of the atmosphere lower in ozone than
the rest of the atmosphere -- then drifts away
from the south polar region as the southern winter
vortex breaks up and air exchange resumes for the
spring, summer and fall.
Answered by: Daniel Rogers, Retired instructor in Environmental Regulation
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