Sea ice Atmosphere Lagrangian Transport of SALT
Part 2: Remote Sensing Measurements of Halogen Oxides
Halogens play an important role in the polar troposphere. Here, they are responsible for the catalytic destruction of ozone in the polar boundary layer, mainly by Bromine but also by Chlorine and Iodine. These so called Ozone Depletion Events (ODE) come along with low temperatures and the reduction of gaseous Mercury in the atmosphere, the so called Atmospheric Mercury Depletion Events (AMDE). The removal of gaseous mercury from the atmosphere leads to a mercury deposition on snow and ice surfaces in the form of particulate and reactive gaseous mercury (PM/RGM). With the melting in summer, mercury enters the food chain and can badly damage the sensitive polar ecosystem.
The mentioned events can be observed in polar spring in the Artic and Antarctic. The origin of the involved halogens is sea salt, whereas the most important halogen Bromine is released into the gas phase by autocatalytic reactions on salty snow and ice surfaces or on aerosols. As a key molecule in all chemical reaction cycles the halogen oxide BrO has been identified. It can be measured from ground and from space via satellite remote sensing by absorption spectroscopy. With the decrease of ozone and gaseous mercury an exponential increase of BrO can be observed, due to the oxidation of Bromine in the responsible chemical reactions. How these so called Bromine explosions are initialized is till now not known in detail.
In the figures above, two example of transport of BrO plumes in polar regions are shown in GOME-2 data
The aim of this project is a better understanding of the initial Bromine release from sea salt. Further, a possible influence of climate change on the chemical processes and for this reason on the strength of Bromine explosions, due to higher temperatures and changes in sea ice cycle, should be analyzed. The needed consistent time series will be obtained from different satellite instruments (GOME, SCIAMACHY, GOME2), which provide continuous observations since 1995. The influence of metrology and chemistry on the release and spreading of Br and BrO will be included by metrological model data, trajectory calculations and a chemistry model.
If you are interested in more information in the SALT project, please contact Mathias Begoin.