UC Irvine

Detailed records of methanesulphonic acid (MSA) and non-sea-salt sulphate (nss SO 4 2− ) have been obtained from ice cores drilled on Dolleman Island on the east coast of the Antarctic Peninsula (70°35.2′S, 60°55.5′W). Annual average concentrations of MSA are presented for the period 1652–1992. Over this time span, the mean annual concentration of MSA is 0.69 μ eq l −1 ( σ = 0.33, n = 340), the range is 0.13–2.35 μ eq l −1 , and the MSA/nss-SO 4 2− ratio is 0.22. The high MSA concentration reflects the proximity of the Weddell Sea, believed to be a region of high marine phytoplankton production. The overall mean nss-SO 4 2− concentration is about 66% of the total sulphate deposited in the snowfall. Low-frequency variations of MSA and oxygen-isotope signals correlate closely, indicating that they may be modulated by similar atmospheric processes. Positive correlations are observed between the oxygen-isotope signature and both MSA ( r = 0.41) and nss SO 4 2− ( r = 0.50), significant at the 99% level. A small negative correlation can be seen between both species and the annual duration of sea ice at Scotia Bay, Laurie Island in the South Orkneys, since 1902 (MSA r = –0.23, and nss SO 4 2– r = –0.29; significant at 95% confidence). No significant link between high MSA concentrations and El Niño events is observed at this location.