INITIAL FINDINGS OF RECENT INVESTIGATIONS OF AIR-SNOW RELATIONSHIPS IN THE SUMMIT REGION OF THE GREENLAND ICE-SHEET

The concentrations of Be-7, Pb-210 and major ions have been measured in aerosol and snow samples collected near Summit, Greenland (72-degrees-20'N, 38-degrees-45'W) in the summers of 1989 and 1990. Comparison to previous results from free tropospheric sampling of the North American Arctic indicates that some aerosol-associated species are as much as 50% depleted in near surface air over the Greenland Ice Sheet. It is shown that local atmospheric processes, particularly isolation of air masses beneath a near surface inversion, can exert dominant influence on the chemistry of surface-level air. These findings illustrate the extreme caution that must be taken if the results of surface-based atmospheric sampling are to be used to examine the relationship between the chemistry of the atmosphere and snow falling from it. Depth profiles of Be-7 in the surface layers of the snowpack near Summit suggest that up to half of the annual accumulation of snow may Occur in the two to three month late spring-early summer period. If this is generally true for the Summit region, previous regional studies of snow chemistry that assumed linear dependence of age on depth to convert depth profiles to time series will have to be reassessed. However, spatial heterogeneity of near surface snow chemistry, that is currently not well understood, makes interpretation of the Be-7 profiles tentative at present.