Chemistry of the sea ice/ snowpack/ atmosphere system in coastal Antarctica

Tropospheric Ozone Depletion Events (ODEs) have been known to occur during springtime in polar regions for over 20 years. During such events, ozone concentrations can fall from background amounts to below instrumental detection limits within a few minutes and remain suppressed for on the order of hours to days. The chemical destruction of ozone is driven by halogens (especially bromine radicals) that have a source associated with the sea ice zone. There is much debate over the source of bromine radicals in the atmosphere that drive polar boundary layer ODEs and few observations of speciated inorganic bromine against which to test current theory. In 2007, year round measurements were made at the British Antarctic Survey station Halley, in coastal Antarctica, using a Chemical Ionisation Mass Spectrometer (CIMS). During specific periods in the spring the CIMS was configured to measure concentrations of BrO, Br2 and BrCl. In addition, concurrent measurements of surface ozone and local meteorology were made. Presented here is an analysis of these datasets in terms of both chemistry, and the broader meteorological situation at play during the onset and termination of ODEs, in a move towards developing a generalised picture for ODEs at Halley. In order to explore halogen release, the MISTRA model is used to consider emissions from specific source regions, identified using HYSPLIT air parcel back trajectories. A new snow-photochemistry module has been developed for MISTRA which includes chemistry which takes place in the liquid like layer on frozen surfaces (MISTRA-SNOW; Thomas et al., 2011). Understanding these surface processes is of great importance to our understanding of the chemistry which initiates a bromine explosion. MISTRA-SNOW is initialised using measurements made at Halley station to explore both the chemical and meteorological conditions required to produce tropospheric ODEs in polar regions.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2014

Author dc:creator

• Buys, Zak

Language dc:language

en