Variable 10Be fluxes in lacustrine sediments from Tristan da Cunha,South Atlantic: a solar record?

A 650-yr-long sediment sequence from a crater lake on Tristan da Cunha, South Atlantic, was analysed for its ¹⁰Be content. Based on ¹⁴C dating, and sedimentary, geochemical, magnetic and palynological records, the period between 900 and 1450 AD appears to have been unusually stable in terms of sedimentation and vegetation and therefore this period was chosen for analysis of the ¹⁰Be content. During this period of highly organic sedimentation and closed vegetation, the pattern of ¹⁰Be flux variations follows the ¹⁰Be fluctuations from the GRIP ice core and estimated ¹⁴C production rates well. However, before and after this stable period, variable sedimentation rates have to be accounted for to obtain results that are comparable to the established ¹⁰Be/¹⁴C records. Our data show not only the possibility of obtaining detailed enough ¹⁰Be flux data from sedimentary sequences to reconstruct past solar forcing but also how sensitive this type of record is to sedimentary and environmental changes. If suitable archives can be found, they have the potential to improve reconstructions of solar activity far back in time.