Atmospheric methane sulfonate and non-sea-salt sulfate records at the European Project for Ice Coring in Antarctica (EPICA) deep-drilling site in Dronning Maud Land, Antarctica

[1] During three summer campaigns in January/February 2000, 2001, and 2002 the ionic composition of the aerosol at the European Project for Ice Coring in Antarctica (EPICA) deep-drilling site at Kohnen Station was measured in daily resolution. In 2000 and 2002 we observed mean (+/- std) non-sea-salt sulfate (nss-SO42-) concentrations of 353 +/- 100 ng m(-3) and 320 +/- 250 ng m(-3), as well as methane sulfonate ( MS) concentrations of 59 +/- 36 ng m(-3) and 74 +/- 80 ng m(-3), respectively. For the summer campaign in 2001, significantly lower nss-SO42- and MS levels of 164 +/- 150 ng m(-3) and 19 +/- 12 ng m(-3), respectively, were typical. The mean MS/nss-SO42- ratio ranged from about 0.1 to 0.2. MS and nss-SO42- concentrations and their variability were roughly comparable to coastal stations at summer. Supported by air mass back trajectory analyses, this finding documented an efficient long-range transport to Kohnen via the free troposphere. MS/nss-SO42- ratios exhibited a strong dependence on the MS concentration with systematically higher ratios at higher MS concentrations, a peculiarity which is also evident in a firn core drilled at this site.