Chemical concentrations were measured using ion chromatography (IC), with an estimated uncertainty on individual measurements of better than 5% (but rather higher at the lowest concentrations seen in interglacial periods). For the upper 580 m, IC Ca was considered unreliable, and Ca measured by continuous flow analysis (CFA) in parallel was substituted (see paper for details). For the IC measurements, samples were collected as the cumulative melt or cut from anything between 5 cm to 1.1 m of ice, and we present averages of 2.2 m increments, and averages of 2000 years.