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 N2, O2 and CO2 in pure clathrate ice in order to determine which layers of an ice core are affected by significant changes in the CO2 concentration and the δ(O 2/N2) ratio for storage durations up to 38 years. The results agree with experimental δ(O2/N2) measurements at ice core pieces performed after different storage durations. Additionally, the calculations confirm the importance of the storage temperature and show that the CO2 concentration is less affected than that of δ(O2/N2). Furthermore, guidelines for ice core sample preparation are provided in dependence of storage duration and temperature. Copyright 2009 by the American Geophysical Union.