TROPOSPHERIC HYDROGEN AND CARBON OXIDES IN ANTARCTICA AND IN GREENLAND

Tropospheric trace gases (H-2, CO, and CO2) were measured in polar are as for two seasons in Antarctica (Italian base Terra Nova Bay) and two in Greenland (European base Summit, Greenland Icecore Program [GRIP]) , yielding the following average concentrations: Antarctica (1989-1990 ): H-2, 528 ppbv; CO, 51 ppbv; CO2, 354 ppmv; Antarctica (1990-1991): H-2, 522; CO, 51; Greenland (1991): H-2, 548; CO, 114; Greenland (1999 ): CO, 107 (hydrogen discarded). Computer automated gas chromatographi c analyses were done in situ using a reduction gas detector (RGD) and a complete set of standards each day, for periods of 2 h in Greenland and 3 h in Antarctica. Approximately 200 analyses were conducted durin g each campaign. Peak areas and standard calibrations in the laborator y were obtained using programs written especially for the purpose. For both Antarctica and Greenland, some differences were found between th e two subsequent seasons; the greatest differences, however, were foun d in Antarctica within the same season (different origins of air masse s). The inter-hemispheric asymmetry is clear and significant. It most likely occurs because pollution from the northern hemisphere reaches t he northernmost regions through the polar vortex, whereas Antarctica i s more isolated by the Southern Ocean.