TRAJECTORY ANALYSIS OF SOURCE REGIONS INFLUENCING THE SOUTH GREENLANDICE-SHEET DURING THE DYE-3 GAS AND AEROSOL SAMPLING PROGRAM

Backward air mass trajectories for Dye 3, Greenland (elevation 2.5 km) show source regions that vary with season: the direction of greatest transport distance is from the southwest in fall, west in winter, and northwest in spring; the trajectories in summer do not show a strong p referred direction. Based on 5 d transit times, the trajectories in fa ll suggest the importance of North America as a potential source regio n, with occasional trajectories from western Europe, The trajectories in spring, especially in April, suggest Eurasia (transport over the Po le), eastern North America, and western Europe as potential source reg ions. Less transport of chemical constituents to Dye 3 is expected in summer when transport distances are shorter. Although some long-range transport to Greenland occurs in winter, the stability of the atmosphe re over the ice sheet at this time of year is likely to limit the deli very of chemical constituents to the surface. Sources outside of these regions can also influence Dye 3 if transit times longer than 5 d are considered. These results are in contrast to trajectories reported by others for sea-level arctic locations such as Barrow, Alaska and Moul d Bay, Canada, where transport over the Pole from Eurasia is responsib le for high chemical species concentrations over much of the winter an d early spring. Overall, the trajectories are consistent with aerosol chemical data for this time period at Dye 3 reported by several invest igators, showing peak concentrations in spring and fall.