CHEMICAL AND METEOROLOGICAL OBSERVATIONS AT ICE CAMP SWAN DURING POLAR SUNRISE EXPERIMENT 1992

Surface mixing ratios of ozone, C-2-C-6 hydrocarbons, and selected org anohalogens were measured at a camp on the Arctic Ocean ice northwest of Ellesmere Island during an 18-day period in April 1992. Ozone was s trongly depleted (at or below instrument detection limits of 0.4 parts per billion by volume (ppbv)) more than 40% of the time and exceeded 20 ppbv only during two brief events, in marked contrast to free tropo spheric mixing ratios of about 45 ppbv observed at Alert. Alkanes, bro moform, and trichloroethylene, which have been reported to be correlat ed with O-3 at Alert, were found to have mixing ratios at the sea ice surface similar to the levels observed during O-3 depletion events at Alert. Meteorological and back-trajectory analyses did not reveal sign ificant correlations with any source region or prevailing local meteor ological condition. Elevated mixing ratios of O-3 and alkanes over the sea ice were associated with periods of increased dynamic mixing or t ransport of air from higher altitudes. Prolonged periods of undetectab le ozone were correlated with air parcels whose trajectories showed th ey had been in close proximity to the surface sometime in the previous five days.