EPICA-Dome C Ice Core FIC Analysis: the Longest Chloride, Nitrate and Sulfate High Resolution Record From an Ice Core (900 kyr).

In the framework of the EPICA project, Fast Ion Chromatographic (FIC) analysis of the 3200 m of the ice core drilled at Dome C yielded a continuous high resolution record of Cl-, NO3- and SO42-, spanning the last 900 kyr and covering the last nine glacial/interglacial cycles. About 140 kdata for each component, with resolutions ranging from 2.0 to 4.0 cm (covering from 1.5 to 50 years), were performed in the field and in the cold laboratory of AWI on continuously melted firn and ice core sections. Cl-, NO3- and SO42- profiles were compared together with the dust and isotopic (dD) smoothed profiles in order to enlighten leads and lags between environmental and climatic changes. Particular attention was devoted to the chemical trend interpretation of the fast climatic variations occurring during the glacial onsets and terminations and the interstadial periods. Since Cl- and NO3- are not irreversibly fixed in the snow layers and can be re-emitted into the atmosphere as gaseous acidic species, their preservation in the snow is affected by accumulation rate and acidity. In particular, the NO3-profile shows a close positive relationship with dust content demonstrating that the acidity neutralization drives the preservation of NO3- in low accumulation periods. Cl-, which are stable for relatively low accumulation rate (higher than 80 kg m-2 yr-1) shows a higher sensitivity to accumulation rate changes. Indeed, high Cl- levels are recorded both in glacial period characterized by high dust content and in high accumulation rate periods such as interglacial climatic optima and interstadials. The SO42- profile is marked by volcanic signatures superimposed to the biogenic background contribution (mainly biogenic). Preliminary evidences showed biogenic SO42- depositional fluxes in the snow was not significantly different in the different climatic stages. In this, way, the SO42- background profile is only tuned by changes in snow accumulation rate constituting a potential proxy-marker for accumulation rate.