Access to the Arctic Ocean

The activation of reactive halogen compounds possibly exerts
the strongest direct link between the sea ice and atmospheric chemistry. More
than 20 years of satellite observations have indicated the regular formation of
bromine oxide in springtime over the Arctic Ocean. Under certain conditions
bromine oxides and possibly other reactive halogen compounds are generated from
sea salt. The halogens have a profound impact on the composition of the
atmosphere leading to the removal of normally ubiquitous ozone and mercury in
the atmospheric boundary layer. At all Arctic coastal stations ozone and
mercury depletion events have been observed regularly. However, the very few
direct measurements of ozone over the sea ice have indicated that the
springtime removal of ozone is more persistent over the Arctic Ocean and
concerns possibly the entire Arctic ocean. The long history of ozone and
mercury observations in the Arctic indicate a complex interplay of chemical,
meteorological, and sea ice conditions for the chemical activation of the
halogens. Nevertheless, the exact conditions still remain unclear. Further in
situ observations in springtime in the boundary layer over the sea ice in
combination with advanced retrievals using remote sensing data are necessary to
improve our understanding of the underlying processes. Only with this knowledge
a better prediction of the impact of the halogens on air quality, short- or
long-lived greenhouse gases like ozone and methane and pollutants like mercury
will be possible.


To perform in situ observations and measurements of
the vertical distribution of reactive species access during all seasons to the
sea ice-covered regions of the Arctic Ocean is urgently needed using ice camps,
ice breakers, and airborne instruments. Instruments and techniques to perform
such measurements have been developed by several French groups and are ready to
be used in the Arctic. Such detailed studies are complementary to satellite
observations and measurements potentially performed within a network of
autonomous buoys and to measurements performed at coastal stations.