During the field campaign Out On The Ice (OOTI) in the spring of 2004 at Alert, Nunavut (N82¿30', W62¿19') an event occurred where surface ozone (O3) and reactive bromine species in the boundary layer showed dramatic changes on a timescale of minutes and a spatial scale of a few kilometers. In apparent direct response to changes in surface wind speed and direction, surface O3 mole fractions of >30 nmol.mol-1 replaced stable, O3 depleted boundary layer conditions for about 5 hours. High time resolved (seconds to minutes) chemical and meteorological observations on the ice and on land, as well as synoptic weather maps and routine radiosonde data are used to constrain the unfolding of the event. It is hypothesized that the bromine oxide (BrO) distribution in the troposphere over the frozen ocean features a maximum in a narrow transition layer that separates the boundary layer from free tropospheric air above.