| Summary: | Surface ozone (03) measurements made between 1997 and 2003 at Arrival Heights, Antarctica (77.8°S, 166.7°E), show sudden decreases in 0 3 mixing ratios during Antarctic springtime. These low 0 3 events are often correlated with elevated concentrations of bromine oxide (BrO). The air mass origin during these 0 3 depletion events was investigated by calculating 5-day back trajectories. Trajectory analysis revealed that air masses had either contact with sea-ice, which was correlated with enhanced BrO columns, or were transported across the Antarctic continent, which led to 0 3 depletion events without elevated BrO concentrations. In 1997-1998 less frequent high BrO events were observed at Arrival Heights probably due to increased sea ice coverage in the Ross Sea during these El Nino years.
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