Elbrus Ice Core, Caucasus record of ammonia (NH4+)

A deep ice core was drilled to bedrock (182.6 m) in 2009 on the western plateau of Mount Elbrus (ELB, 43°N, 42°E; 5115 m above sea level, asl) in the Caucasus (Russia). The upper 168.6 m (131.5 meters water equivalent, mwe) depth of the ice core were first dated by annual layer counting using pronounced seasonal variations in ammonium and succinate concentrations, both exhibiting well-marked winter minima (Mikhalenko et al., 2015; Preunkert et al., 2019). Chemical measurements were done with a Dionex ICS-1000 chromatograph equipped with a CS12 separator column for cations (Na⁺, K⁺, Mg²⁺, Ca²⁺, and NH₄⁺), a Dionex 600 equipped with an AS11 separator column for anions (Cl^-, NO₃^-, and SO₄^2-) and light carboxylates. Detailed working conditions are given in Legrand et al. (2013). Using the winter ammonium/succinate minima we determined half-year summer and winter means of of ammonia (NH4+) from 1748 to 2009.