ICE CORE RECORD OF CO VARIATIONS DURING THE LAST 2 MILLENNIA - ATMOSPHERIC IMPLICATIONS AND CHEMICAL INTERACTIONS WITHIN THE GREENLAND ICE

In order to study in detail the pre-industrial CO level during the las t two millennia and its temporal variations, several ice cores from Gr eenland and Antarctica were analysed. Our Antarctic CO results remain very close to those observed previously for the last 150 years and sug gest that carbon monoxide concentration did not change greatly over An tarctica during the last two millennia. Between 1600 and 1800 AD, CO c oncentrations obtained in the Greenland ice are also very close to tho se already reported for the 1800-1850 AD period. In contrast, the olde st part of the Greenland CO profile exhibits high CO levels (100-180 p pbv) characterised by a strong variability. This part of the Greenland record likely does not reflect the true atmospheric CO concentrations . We discuss the possible processes which could have altered the atmos pheric CO signal either before or after its trapping in the ice. The o xidation of organic material in the oldest part of the investigated Gr eenland ice appears as the most likely explanation. Because there are strong similarities between the Greenland CO and CO2 concentration pro files for the 1000-1600 AD period, mechanisms involved in both cases c ould be at least partly the same. Therefore, oxidation of organic mate rials is a serious candidate for in-situ CO2 production in the Greenla nd ice. Due to the fact that the Antarctic ice contains much less impu rities and show no peculiar variability in CO concentrations, we are m ore confident about the atmospheric significance of our Antarctic CO c oncentration profile.