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A continuous melting technique, combined with continuous flow analysis, has been developed for in situ measurements of chemical trace species in ice cores. A crosssection of 1.8 X 1.8 cm2 of the core is needed for the simultaneous analysis of at least four species. The subcore is melted continuously from one side, and only the inner, uncontaminated part of the melted sample is used for the analysis. The main advantage of this method as compared to conventional sampling and analysis procedures is given by a very high spatial resolution, combined with a significant reduction of sample handling work. The method can be applied for any species for which a sensitive continuous flow analysis method exists. This technique has been applied successfully for the parallel measurement of H2O2, HCHO, NH4+, and Ca2+ during the Greenland Ice Core Project (GRIP) deep drilling project at Summit, central Greenland (72°34' N, 37°38' W, 3200 m above mean sea level).

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H2O2 analyses of polar ice cores show an increase in concentration from 200 years to the present. In order to quantitatively relate the observed trend in the ice to atmospheric levels, the atmosphere‐snow transfer behavior and postdepositional changes must be known. Atmosphere‐snow transfer was studied by investigating uptake and release of H2O2 in a series of laboratory column experiments in the temperature range −3°C to −45°C. Experiments consisted of passing H2O2‐containing air through a column packed with 200‐μm diameter ice spheres and measuring the change in gas phase H2O2 concentration with time. The uptake of H2O2 was a slow process requiring several hours to reach equilibrium. Uptake involved incorporation of H2O2 into the bulk ice as well as surface accumulation. The amount of H2O2 taken up by the ice was greater at the lower temperatures. The sticking coefficient for H2O2 on ice in the same experiments was estimated to be of the order of 0.02 to 0.5. Release of H2O2 from the ice occurred upon passing H2O2‐free air through the packed columns, with the time scale for degassing similar to that for uptake. These results suggest that systematic losses of H2O2 from polar snow could occur under similar conditions, when atmospheric concentrations of H2O2 are low, that is, in the winter.

The air trapped in the bubbles of natural ice is not the same age as the surrounding ice. This is d ue to the fact that the air is enclosed in isolated bubbles only at the depth of the firn-ice transition. Within the overlying porous firn layer the air is able to mix and to exchange to a certain degree with the atmosphere. The age difference between ice and air is given by the age of the ice at pore close-off, less the mixing delay. Also, there is an age distribution due to diffusive smoothing and due to the gradual enclosure of the air at the firn-ice transition. Knowledge of this age relation is necessary for the interpretation of climatic parameters measured on ice cores. This work concentrates on the effect of diffusive mixing. We report on measurements of the diffusivity of CO 2 and 02