Ice-core cosmogenic radionuclides support the occurrence of an extreme solar particle storm 5259 BCE (7208 years BP).

A prominent rapid increase in radiocarbon from tree rings has been detected in 5259 BCE (7208 years BP). In this study, we present 10Be and 36Cl data from the NGRIP and the GRIP ice cores from Greenland, and the EDML ice core from Antarctica around the 14C excursion. The ice-core radionuclide data show an increase consistent with the occurrence of an extreme solar energetic particle (SEP) event. The 10Be data show the event was of a similar magnitude as the extreme SEP event of 7176 BCE (9125 years BP), in agreement with previously published 14C data. Using all ice-core radionuclide data, we show that the event was characterized by a fluence above 200 MeV comparable with that of other extreme SEP events detected in radionuclide records. In addition, the detection of the SEP event in both tree-ring and ice-core records provides an important time-marker to synchronize the ice-core and tree-ring chronologies. This article is part of the Theo Murphy meeting issue 'Radiocarbon and cosmic radiation events'.