Tim Hay
Bromine explosions and ozone depletion in McMurdo Sound
Tim Hay, Department of Physics and Astronomy
Supervisors
Adrian McDonald, Department of Physics and Astronomy
Peyman Zawar-Reza, Department of Geography
External Supervisors
Karin Kreher, NIWA
Robyn Schofield, Alfred Wegener Institute, Germany
Springtime ozone depletion events in the polar marine boundary layer were first observed in the mid 1980's. It is now widely accepted that the main mechanism for these tropospheric ozone depletion events involves autocatalytic release of bromine from sea-salt, referred to as bromine explosions. The conditions that trigger these events are not yet fully understood, but the presence of first-year sea ice and an inversion layer, which acts as a barrier permitting little exchange with the air above, are known to be important.
The aim of this research is to observe these events using portable instrumentation at various sites on the sea ice in McMurdo Sound . Atmospheric BrO (bromine monoxide) and IO (iodine monoxide) were measured using a spectrometer, while surface atmospheric ozone and meteorology were also monitored. Several ozone depletion events along with elevated boundary layer BrO were observed during the 2006 and 2007 measurement periods. Enhanced IO was also observed at Cape Bird . Air mass back trajectories indicate that these relatively small events were locally produced rather than involving transport across extensive sea ice regions to the North. A new radiative transfer model and modified optimal estimation retrieval code has been developed. This enables more accurate information on diurnal variation and vertical concentration profiles to be obtained from the spectrometer measurements. This research is part of a NIWA project.
Publications
Hay, T.D.; Kreher, K.; Johnston, P.; Thomas, A.; Riedel.K.; Schofield.R:, McDonald, A. (2008). 4th International DOAS workshop for Environmental Research and Monitoring, Springtime MAX-DOAS measurements of bromine explosion events on the sea ice in Antarctica, Hefei , China , April 2008.
Hay, T.D.; Kreher,K.; Riedel, K. (2007). Bromine explosions and Antarctic ozone. Water and Atmosphere 15(2), 12-13.