Past atmospheric composition and climate, gas parameters measured on ice cores

Variations of physical and chemical properties of ice cores have been observed by many authors (1–3). These variations could be attributed to temperature effects, different origins of moisture and changes in concentrations and isotopic composition of atmospheric constituents. We report here data from parameters measured in a section of the Camp Century ice core from Greenland. Gas content and composition were measured systematically in a continuous set of samples covering ∼2 yr of precipitation. The data are compared with measurements of 18O/16O ratio, electrical conductivity, pH values and crystal size. The aim of the investigation was to determine which parameters show random and which seasonal variations. Special consideration is given to the CO2 content, which is higher in the gas extracted from natural ice than in the atmosphere (4) and shows short-term variations which cannot be explained by variations of the atmospheric CO2 content alone. These probably reflect variations in the meteorological conditions at the time of precipitation. Meterological conditions may influence other parameters of the ice in a similar way. If such correlations could be found, one might be able to correct the observed CO2 variations for the meterological effect and sort out the effect related to changes in the atmospheric CO2 content. Measurements of the CO2 content of ice cores of different age could then be used to reconstruct the history of the atmospheric CO2 content from present to 100,000 yr BP.