Causes and timing of the 8200 yr BP event inferred from the comparison of the GRIP 10Be and the tree ring Δ 14C record

Abstract

We analyse the 8200 yr BP cold event by comparing the high-resolution 10Be record from the GRIP ice core from Central Greenland with the well-known tree ring Δ 14 C record. By transferring the absolute dated tree ring chronology to the ice core time scale, we show that the coldest phase in the GRIP record occurred around 8150 yr BP. Furthermore, this method allows us to disentangle production and climate effects on 10Be and 14C with important implications for the reconstruction of past solar activity, and changes in the carbon cycle and 10Be transport. We show that, in principle, it is possible to infer changes in ocean circulation by comparing 10Be and 14C records. However, the duration of the 8200 yr BP event is too short to assign unambiguously a significant change in atmospheric 14C concentration to changes in the global ocean circulation. Based on the comparison of 10Be with climate records, one could argue that the 8200 yr BP cold event is triggered by a change towards lower solar activity. However, this link is questioned by the fact that around this period there are other similar and even stronger changes in solar activity that have no apparent connection to climate changes.