British Antarctic Survey ozone report 1993 October 18

Preliminary ozone values from the British Antarctic Survey
Faraday station (65 south, 64 west on the coast of the
Antarctic Peninsula) show running average ozone values
dropping from around 280 DU at the begining of September to
around 200 DU at the month's end.  There is considerable day
to day variation.  Data from our long term record for the
station indicate normal values of around 330 DU for this
period (with a range of 280 DU to 380 DU).  This year's mean
September ozone value is 245 DU, giving a reduction of about
25%.  The minimum September daily mean value of 142 DU on
September 28th is the lowest ever recorded at Faraday (next
lowest 145 DU in 1992).

Preliminary ozone values from the British Antarctic Survey
Halley station (76 south, 26 west on the Brunt ice shelf) show
mean ozone values dropping from around 210 DU in early
September to around 110 DU in early October.  Data from our
long term record for the station indicate normal values of
around 300 DU for this period (with a range of 260 DU to 340
DU).  This year's mean September ozone value of 159 DU is the
second lowest recorded at Halley (lowest 146 DU in 1992),
giving a reduction of around 35%.  The minimum September daily
mean value of 108 DU on September 30 is the lowest recorded at
Halley (next lowest 111 DU in 1992).  Ozone levels in early
October are the lowest ever recorded with depletion exceeding
two thirds.

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Additional report:
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Record low ozone in Antarctica


This  year's Antarctic ozone hole (1993) is the deepest ever.
Scientists of the British Antarctic Survey (BAS) at Halley
Research Station  in Antarctica have recorded their lowest
ever value of  ozone, showing that over two-thirds of the
protective ozone shield  has been  destroyed.  Less than one-
third remains intact, and  the depletion  phase may not be
over for some days yet.  BAS scientists at Faraday Research
Station, normally near the  edge of the ozone hole, have also
measured record low values of ozone for their station.

The Antarctic  ozone hole  is an  annual phenomenon  which
has occurred in  every (southern  hemisphere) spring since the
late 1970s.   It is  caused by  the chemical  action of
chlorine and bromine released  from man-made
chlorofluorocarbons (CFCs) and halons.   Thanks to  the
international  Montreal Protocol,  the annual production  of
these substances is now less than before, but the  total
amount  in the  atmosphere  continues  to  rise, dashing hopes
of an  early recovery  for the ozone layer.  The CFCs are  not
expected  to reach their maximum concentration in the
atmosphere  until around  the turn  of the  century, so the
Antarctic ozone hole may continue to worsen until then.

BAS scientists  have been  measuring ozone  in Antarctica  on
a daily basis  since 1957.   There was no ozone hole at all
until the late  1970s.   The Antarctic ozone layer is not
expected to return to  normal until the 2070s.

Jonathan Shanklin