Measurements from the Global Ozone Monitoring Experiment GOME have been analysed for tropospheric BrO in the northern hemispheric spring and summer 1997. Tropospheric excess columns have been determined by subtracting measurements from a longitude range which is assumed to represent background conditions. From February until the end of May enhanced tropospheric BrO columns are observed over the Hudson Bay area and parts of the Canadian Arctic. This large and persistent event has not been reported before and can only be explained by a large local source of bromine. In addition, from March to May other smaller and shorter tropospheric BrO events are detectable along the coast lines of the Arctic Sea and over the polar ice. They correspond to the ground-based observations of enhanced tropospheric BrO reported from several stations in the high Arctic. ¿ 1998 American Geophysical Union