NorthGRIP ice-core record of major ions measured using ion chromatography covering the last two millennia and additional short Holocene sections

Ion concentration data was obtained from the NGRIP1 ice core drilled in 1996 and 1997. NGRIP1 camp position 75.1N, 42.32W. All samples were cut and decontaminated using a microtome knife in a laminar-flow bench at the field site. In 1996, the 9.850 – 349.250 meter depth interval was cut continuously in 5 cm resolution. In 1997, selected sections from the Holocene, mainly containing volcanic signals, were cut in 5 cm or 2.5 cm depth resolution. Samples covering the 8.2 ka BP cold event were cut from the depth interval 1221-1237.5 m. The frozen samples were thawed in the laboratory and immediately after poured into sample vials for ion chromatography analyses. Bags 212-403 were measured in Department of Physical Geography, Stockholm University, Sweden. The rest of the samples were measured at the Geophysics Department, Niels Bohr Institute, University of Copenhagen, Denmark, on a Dionex 500 IC. The data are labeled “Sto” and “Cph” for samples analysed respectively in Stockholm and Copenhagen. Data measured in Stockholm were calibrated to a calibration curve established using eight standards, while data measured in Copenhagen were calibrated to a linear calibration curve established using a single standard. Ammonium concentrations measured in Copenhagen may be biased due to possible sample uptake of Ammonium from the air while in the liquid phase. In Stockholm, Li⁺ was not measured and F⁻ -concentrations may be biased due to methods that was not optimal for quantification of fast eluted ions. All values are ion concentrations given in µeq/L (micro-equivalent per liter melted ice). Data were collated November 2000 by Marie-Louise Siggaard-Andersen. Samples that are labeled PID (Possible Improper Decontamination) was marked in the field in cases where proper decontamination could be questioned. However, the amount of contamination is limited because the samples were in a solid state and the environment was very clean. Samples labeled PCL (Possible Contamination in the Liquid phase) was marked in the laboratory or during data evaluation in cases where contamination could be questioned. Samples labeled “remeasured” have been measured from a portion of the sample that has been kept in liquid state for several hours after thawing. The organic acids, formic acid and acetic acid, were measured but not quantified. A few sample are labeled “Organic Acid” because significant large amounts was observed in the chromatograms. The data file is released in connection with the ESSD paper of Rasmussen et al. (2022). Information about analysis setup can be found in Littot et al. (2002), Siggaard-Andersen et al. (2002), and Jonsell et al., (2007)