On the Atmospheric Transport and Deposition of the Cosmogenic Radionuclides (10Be): A Review

Cosmogenic radionuclides, such as Be-10, are commonly used for reconstructing solar activity in the past. The interpretation of Be-10 records, most commonly obtained from polar ice cores, is complicated by the mixing of Be-10 in the atmosphere, its transport to polar regions and its deposition. Throughout the generations of Be-10 studies these complications have been mentioned but never investigated on a physical basis. This manuscript aims to summarize the recent efforts to study the atmospheric transport of Be-10 from its production to its deposition into the polar ice using three-dimensional physically based general circulation models (GCMs) of the atmosphere. These models represent our best understanding of the atmospheric processes up to date. The model studies indicate that the most important factor controlling the deposition response of Be-10 to production changes is the fact that a major part of it (similar to 65%) is produced in the stratosphere where its residence time is long and it undergoes strong mixing. Therefore, in an ideal archive the Be-10 concentrations will reflect the global mean production rate and hence changes in the solar activity. An explanation is offered for the partly different deposition responses of Be-10 snow concentrations to production changes obtained with two different GCMs.