THE DYE-3 GAS AND AEROSOL SAMPLING PROGRAM (DGASP) - AN OVERVIEW

DGASP was designed as an international effort to study the processes i nfluencing chemical species that eventually reach the deep ice in the south of Greenland. These processes include long-range atmospheric tra nsport, wet and dry deposition to the snow surface, and changes during aging of the snow. The program took place during August 1988-July 198 9. Experimental work included sampling of aerosols and gases, collecti on of fresh and older surface snow, and sampling of snowpits. The vari ous samples were analysed for chemical species that are tracers of spe cific source categories. Results of the program show that the southern Greenland Ice Sheet experiences very different airborne concentration patterns than sea-level arctic sites. Concentrations of SO42-, trace metals, and other species are episodic and peak in April, unlike the c onsistently high concentrations during January-April seen at lower ele vations. Source regions influencing Dye 3 are variable, and include No rth America, western Europe, and the Arctic Basin. The last region is particularly important, as it may contain relatively high concentratio ns of chemical constituents from eastern Europe and western Asia that eventually reach Dye 3. The seasonal variations in airborne concentrat ions are generally also reflected in fresh snow. Similarly, these patt erns are seen in snowpits, although some modifications to the glacial record are apparent. Other information on the extent of riming, aeroso l/gas partitioning, and aerosol size distributions demonstrate the com plexity of air-snow transfer processes, and illustrate the need for fu rther research.