900 kyr of Paleo-Volcanism From the EPICA Ice Core (Dome C - Antarctica).

In the framework of the EPICA program (European Project for Ice Coring in Antarctica), a deep ice core was drilled at Dome C (East Antarctic Plateau) reaching the depth of about 3200 (corresponding to about 900,000 years) at the end of the '02-'03 drilling season. High-resolution measurements of sulfate (every 1.5-2 cm, corresponding to 1-50 years depending on depth) were carried out by Fast Ion Chromatography (FIC) directly in the field, allowing the reconstruction of the paleo-volcanism from the Dome C record covering the last 9 glacial cycles. The volcanic signatures were distinguished from the biogenic sulfate background by evaluating a threshold by a statistical approach. For the last millennium the Dome C volcanic record was compared with those coming from several Antarctic ice cores, and differences in the depositional fluxes of the events memorized at different sites were interpreted in terms of changes in snow accumulation rate and atmospheric circulation. For older ages, the correlation between changes in the frequency of volcanic signatures and climatic proxies (such as dD) was carried out aiming to enlighten possible links between climatic changes and volcanism. The sharp decrease of the event frequencies recorded in the deeper part of the core is interpreted in terms of both a decrease of temporal resolution and diffusion of sulfate in the ice. Anomalously high sulfate spikes recorded in the deepest part of the ice core could be interpreted as the effect of depositional processes of local-volcanism products coupled with dust spikes able to prevent the sulfate diffusion or caused by aggregation processes of non-volcanic sulfate-salt particles.