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

Abstract

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 atmosphere⁴ 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.