Ozone depletion events in the polar troposphere have been linked to extremely high concentrations of bromine, known as bromine explosion events. On April 4-5, 2011, we observed such an event in the Canadian High Arctic at the Polar Environment Atmospheric Research Laboratory (PEARL, 86.4°W, 80.1°N), with measurements made by a UV-visible spectrometer showing that the surface volume mixing ratio of BrO increased from ~1 to ~20 pptv. Ozone, measured by ozonesondes, was depleted to ~1 ppbv from the surface to 720 m during this event. Zenith Scattered Light Differential Optical Absorption Spectroscopy (ZSL-DOAS) and Multi-Axis DOAS (MAX-DOAS) data have been used to retrieve stratospheric and tropospheric BrO profiles and partial columns. GOME-2 tropospheric columns of BrO have been used to complement the ground-based measurements.
The HYSPLIT back-trajectory model and GOME-2 data confirmed that this event originated over the Beaufort Sea on March 31, 2011. The interim reanalysis meteorological data from the European Centre for Medium-Range Weather Forecasts (ECMWF), indicates that the 10-m wind increased from 5 to 24 m/s and the boundary layer height surged from 180 to 610 m over Beaufort Sea during the bromine explosion event, suggesting that it was generated from unstable boundary layer meteorological conditions. Further evidences show this long distance (over ~1,800 km) transport event lasted for more than four days, which indicates a strong recycling of BrO within the bromine cloud. The observed bromine explosion event was captured by the UMUKCA chemistry-climate model, which calculated a surface bromine surge to ~10 pptv and surface ozone depletion to ~1 ppbv at PEARL. Comparisons between the measurements and model show that the bromine depletion factor used in the blowing snow bromine release mechanism requires further investigation.