Supplementary material to "Imprint of Arctic sea ice cover in North-Greenland ice cores"

Abstract

Supplementary information for Imprint of sea ice cover in North-Greenland ice cores by Della Lunga et al., 2019 Methodology The methods involved in the measurement of B26 ionic species are extensively described in Sommer (1996) and only briefly summarized here. Ions were measured at Heidelberg University utilizing a Dionex 300 Ion Chromatographer with CS12 separation column in isocratic configuration run (15 minutes) measuring Ca 2+ , Mg 2+ , K + , NH4 + and Na + , while anions (F -, Cl -, SO4 2-, Br -, NO3and MSA) were measured with a Dionex 4500i Ion Chromatograph with a AS11 separation column in a gradient configuration run (16 minutes), with reported limit of Detection (LOD) of 0.1-0.4 ppb for all elements.All B17 discrete samples were analyzed at Alfred Wegener Institute in 2018. Given the melting speed of 2.8-3.5 cm/min and an average layer thickness (λ) of ca. 11 cm during the B17 melting campaign in Bern, the resulting sampling resolution was 2-6 samples per year. All samples were analysed by Capillary Ion Chromatography (Dionex ICS-5000+ HPIC) in a suppressed, reagent-free system and isocratic elution configuration that utilizes an IonPac AS18-Fast column (150 x 2 mm i.d.) for anions (F -, Cl -, SO4 2-, Br -, NO3and MSA) and a IonPac CS12A column for cations (Ca 2+ , Mg 2+ , K + , NH4 + and Na + ) measurements. Accuracy has been calculated as relative standard deviation (in %) of ionic species measured in Milli-Q © water collected during the B17 melting campaign and it is defined as:where σ is standard deviation and µ is the mean of concentration of ionic species I in Milli-Q © water.Similarly, precision has been calculated as the average of the relative standard deviation of ionic species measured in Milli-Q © water by Ion Chromatography and nominal values for Milli-Q © water reported in (Kano et al., 2004) and it is defined as:where n is the number of measurements, σ is again standard deviation and xi is the nominal concentration of the species i in Milli-Q © water as in (Kano et al., 2004).Overall reproducibility (precision) and accuracy are 0.05% and 0.01% RSD respectively, maintaining the sensitivity of the conductivity detector in the range of 0.2-0.5 nS·ng·g -1 , resulting in a Limit of Detection (LOD) between 0.07 and 0.1 ng·g -1 for most elements. Limit of Detection for each element has been calculated as in Hubaux & Vos (1970).