SULFUR-CONTAINING SPECIES (METHANESULFONATE AND SO4) OVER THE LAST CLIMATIC CYCLE IN THE GREENLAND ICE CORE PROJECT (CENTRAL GREENLAND) ICECORE

A high-resolution profile covering the last two centuries and a discon tinuous study spanning the complete last glacial-interglacial cycle of methanesulfonate (MSA) (CH,SO,) and sulfate were obtained along Summi t (central Greenland) ice cores. MSA concentrations were close to 4 +/ - 1.4-ng g(-1) from 1770 to 1870 A.D. and 3 ng g(-1) in 1900, and exhi bited a well-marked decreasing trend from 1945 to the present. These c hanges of Summit snow MSA concentrations between 1770 and 1945 are dis cussed in terms of possible modulation of dimethylsulfide (DMS) marine emissions influencing the Greenland Ice Sheet by past climatic fluctu ations in these regions. The decrease of MSA levels in Summit snow lay ers deposited since 1945 suggests either a decline in marine biota at high northern latitudes or a changing yield of MSA from DMS oxidation driven by modification of the oxidative capacity of the atmosphere in response to increasing anthropogenic NO, and hydrocarbon emissions. Wh ile interglacial ice concentrations of MSA and sulfate are close to 2. 9 +/- 1.9 ng g(-1) and 27 +/- 10 ng g(-1), respectively, reduced MSA ( 1.2 +/- 0.7 ng g(-1)) and enhanced sulfate (55 +/- 19 ng g(-1)) levels characterized the early Holocene stage (9000 to 11,000 years B.P.). M SA concentrations in glacial ice remain similar to the ones observed d uring interglacial stages. In contrast, sulfate levels are strongly en hanced (243 +/- 84 ng g(-1)) during the last glacial maximum (14,400 t o 15,700 B.P.) compared with the interglacial ones. These variations o f sulfur-containing species in response to past climatic conditions ar e similar to those found in other Greenland cores. In contrast, they a re different from those revealed in the Antarctic Vostok ice core, whe re colder climates were associated with an increase by a factor of 5 a nd 2 in MSA and sulfate concentrations, respectively. These glacial-in terglacial changes are discussed in terms of present and past contribu tions of marine DMS emissions versus other sulfate sources such as vol canic emissions and continental dust to the Greenland precipitation.