Episodic bromine enhancement occurs over first year sea ice zones during spring, with corresponding rapid decreases in surface ozone concentrations. The release of bromine via autocatalytic heterogeneous reactions on sea-salt surfaces, including young sea ice, snow pack and aerosols, is known as a 'bromine explosion'. With the return of sunlight in spring, the rate of bromine photolysis rapidly increases, and the rresulting bromide ions react with ozone to form bromine monoxide (BrO). A frequent stable inversion layer concentrates BrO near the surface and prevents replenishment of ozone from the overlying free troposphere, resulting in rapid ozone depletion.BrO measurements have been made at Arrival Heights using zenith-sky UV- visible differential optical absorption spectroscopy (DOAS) since 1995 and multi-axis (Max-) DOAS since 1998.