| Summary: | The impurity and stable isotope in water records extracted from the Colle Gnieffti ice core (Swiss-Italian Alps, 45°55′50″N, 7°52′33″E, 4455 m asl) contain information on the composition of the past atmosphere and climate conditions over the Holocene. Here we provide annual mean concentrations of major ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3-, SO42-), refractory black carbon (rBC) and trace elements (Al, Mn, Fe, Sr, Rb, V, Cr, Ba, Pb, Bi, Cd) next to the isotopic composition of water (i.e. d18O) from a stack of 2 firn cores drilled in 2008 and 2015 (CG15, CG08) and two parallel deep ice cores drilled in 2003 (CG03A, CG03B) encompassing the period 950 to 2015 CE. Major ions were determined at the Paul Scherrer Institute using ion chromatography (with Dionex and Metrohm systems) and rBC was analyzed with a Single Particle Soot Photometer (SP2, Droplet Measurement Technologies) and a jet (APEX-Q, Elemental Scientific Inc.) nebulizer to aerosolize the aqueous samples (Sigl et al., 2018). Trace elements were analyzed at the University of Venice using a continuous ice- core melting device coupled to an Agilent 7500 quadrupole inductively coupled plasma mass spectrometer (ICP-Q-MS) and a Element2 (Thermo-Finnigan) sector field inductively coupled plasma mass spectrometer (ICP-SFMS) with discrete sampling (Gabrieli et al., 2011, 2014; Sigl et al., 2018). Stable isotopes of water were measured at the Paul Scherrer Institute by isotope ratio mass spectrometry (IRMS) using a Delta Plus XP (Finnigan MAT) system. Analytical uncertainties were ±0.1 ‰ for d18O. Annual mean concentrations and the mean annual isotopic composition of the water were calculated by averaging all samples within each year. Samples below the detection limit were set to 50 % of the value of the detection limit. Ice-core dating is based between 1763 and 2015 CE on annual-layer counting, constrained by historic Saharan dust events and volcanic eruption signals. Before 1741 CE the dating is based on a simple glacier flow model fitted to radiocarbon dates ...
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