Change in CO₂ concentration and O₂/N₂ ratio in ice cores due to molecular diffusion

Abstract

Polar ice cores are unique archives for ancient air. However, a loss of air due to molecular diffusion during storage could affect the composition of the remaining air. We formulate a model with a high spatial resolution (1 mm) calculating the loss of N 2 , O 2 and CO 2 in pure clathrate ice in order to determine which layers of an ice core are affected by significant changes in the CO 2 concentration and the δ (O 2 /N 2 ) ratio for storage durations up to 38 years. The results agree with experimental δ (O 2 /N 2 ) measurements at ice core pieces performed after different storage durations. Additionally, the calculations confirm the importance of the storage temperature and show that the CO 2 concentration is less affected than that of δ (O 2 /N 2 ). Furthermore, guidelines for ice core sample preparation are provided in dependence of storage duration and temperature.