| Summary: | Information on the history of the atmospheric CO2 content and the 2SC/12 and 14C/C ratios is recorded in natural ice. Measurements on samples from very cold accumulation regions show that CO2 is occluded not only in air bubbles, but also in the ice lattice. The two CO2 components are of similar size. It is very difficult to measure CO2 in the bubbles and CO2 in the ice lattice separately. By melting the samples and extracting the evolving gases in two fractions, it is possible to estimate CO2 concentration in the bubbles and the ice lattice. Enrichment or depletion of CO2 in the bubbles by exchange with the ice is difficult to estimate. Information about this effect is expected from 13C/12C analysis on the extracted CO2 fractions. To investigate whether atmospheric CO2 content was different during the last glaciation than during the present one, sets of 16 and 20 samples distributed over the last 40,000 years from the two deep ice cores from Camp Century (North Greenland) and Byrd Station (West Antarctica) were measured. The time scales for the two cores -are Tbahsee dd aotna ase rrhieeso lforogmica bl omtho dceol.r eRs esshuolwts sainmdi lcaor ntcrleunsdiosn cso arrreel: ated to a certain degree to - tFhoer 5b7o8t0h pcroorfeilse, s.t he values for the CO2 concentration of the first fraction, considered to best represent the atmospheric composition, show lower values during glaciation - tLhoawn CinO 2t hceo nHcoelnotcraetnieo,n ws iinth tha em fiinrsitm furamct iboenfso r(e2 00thpep men) do fo cf egrltaacinia stiaomnp. les are a strong indication that the atmospheric CO2 concentration during last glaciation was lower than during the postglacial. These low concentrations indicate that, at that time, CO2 concentration in the atmosphere could have been lower than today by a factor of 1.5. Possible explanations for such a change in atmospheric CO., content as well as its influence on atmospheric 14C/C ratio and on the radiation balance is discussed.
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