Environmental Engineering Reference
In-Depth Information
such future eruptions would occur in the tropics. The resulting global estimate would
be one
'
large stratosphere-endangering
'
subduction-zone eruption in the tropics every
200 to 400 years. Indeed, the last
~
150 years were a rather quiet period concerning
explosive volcanic activity compared to other periods, such as, for example,
1780
-
1850 (Lamb,
1970
). In addition to a lack of available measurements, this may
be a reason why there has been a gap in halogen-rich, ozone-depleting volcanic
eruptions in the tropics during the past 150 years.
16.7 Summary
The effect of volcanic halogen release from present-day eruptions on the ozone
layer is often neglected as it is believed not to play a significant role. This view
may, however, change during the next large and halogen-rich volcanic eruption in
the tropics, especially when considering the current decline of anthropogenic Cl
loading in the twenty-
rst century back to pre-ozone hole conditions.
Since El Chichon 1982 and Pinatubo 1991, no large, sulfur-rich eruption
took place in the tropics impacting climate globally, but statistically it could
happen any day, given the above discussion. Measurement techniques have been
signi
cantly improved over the last decades, now enabling the detection of vol-
canic Br in extremely low concentration range (ppt) (see also
Chapter 8
). Future
research should take into account the likelihood of volcanic halogen entrainment
to the stratosphere and prepare
in situ
and satellite measurement techniques as well
as chemistry climate modelling for these explosive events. Improving the under-
standing of natural, external climate factors is of importance for the present and
future development of the ozone layer, especially during the current decline of
the anthropogenic Cl background levels.
Acknowledgements
We would like to thank Steven Montzka and Guus Velders for providing the data
for the halogen and EESC projections from the 2010 WMO ozone assessment; and
our colleagues from the SFB574 in particular Armin Freundt, Heidi Wehrmann,
Wendy Planert-Perez as well as Karen Appel from DESY Hamburg for carrying out
the intensive
field and lab measurements. Part of this work was carried out within the
SFB574 (DFG) project
'
Volatiles and Fluids in Subduction Zones
'
at Kiel University.
References
Aiuppa, A., Federico, C., Franco, A.
et al
., 2005, Emission of bromine and iodine from
Mount Etna volcano,
Geochem. Geophys. Geosys
., 6, Q08008.
Aiuppa, A., Baker, D.R. and Webster, J.D., 2009, Halogens in volcanic systems,
Chem.
Geol
., 263,1
-
18.
