The Atmosphere

Tropospheric Ozone Depletion and Bromine Explosions

Principal Investigator: Karin Kreher and Katja Riedel
Organisation: NIWA

What we do: This programme aims to determine the relationship between sea ice surfaces, bromine oxide (BrO) production and ozone depletion. It is linked with the international programme “Air-Ice Chemical Interactions – IPY coordinated studies”. We believe that some ozone depletion and bromine explosion events might go unnoticed at Arrival Heights due to the elevation and distance of the observatory from the sea ice. We have therefore developed a mobile observation platform to measure near-surface BrO and ozone concentrations and vertical profiles. These measurements were performed on the sea ice just below Arrival Heights and at Cape Bird during spring 2006. For 2007, the mobile platform is currently located close to Inaccessible Island and will again be moved to Cape Bird later during this season.   

Why we do it: Near-surface ozone depletion events (not to be confused with the ozone hole in the stratosphere) occur regularly in the Antarctic springtime. It has been confirmed that the sudden release of bromine compounds from seas salt (in so-called bromine explosion events) is responsible for the observed destruction of ozone. However, the conditions that trigger these events are not yet fully understood. We know that first-year sea ice is playing a major role but we don’t yet understand the exact details, e.g. the importance of frost flowers for the release mechanism is currently very controversial. 

What we have found out so far: We detected two ozone depletion events on the sea ice during the 2006 campaign, including one that the instruments at Arrival Heights missed. Preliminary analysis indicated elevated BrO levels in the boundary layer during these events. Satellite images also showed elevated BrO over the Ross Sea region on these days.

Recent Publications:
Simpson, W.R, von Glasow, R. Riedel, K. et al. 2007. Halogens and their role in polar boundary-layer ozone depletions. Atmos. Chem. Phys. 7: 4375-4418. Link to Abstract.