10Be in lacustrine sediments—A record of solar activity?

Abstract

Concentrations and fluxes of cosmogenic 10Be in three varved lake sediments covering the last 100 years were determined to investigate their suitability to record past solar activity. The 10Be signal in lake sediments is composed of a component reflecting the radionuclide production in the atmosphere and a component related to the subsequent transport into the sediment. In order to separate these two components we applied singular-spectrum analysis (SSA). The extracted patterns in concentrations and depositional fluxes were compared to 10Be records from polar ice cores and to the solar modulation potential derived from neutron monitor data. In the transport component we discovered the existence of a long-term trend in the 10Be concentrations, which can be attributed to the redox cycle of both lakes. In the production component we found a similar pattern as in the NGrip ice core. A cross-correlation analysis yielded a significant negative correlation between the 10Be production component and the solar modulation potential. 10Be lags the production on average by 1.5 years which corresponds to the expected transport time from the atmosphere to the Earth's surface. Hence, we conclude that varved lake sediments are potentially suitable to study the solar activity of the past. However, one should be aware that various mechanisms may mask the 10Be signal in the sediment.