Sulfate concentration and sulfur isotope data from Greenland TUNU2013 ice-core samples between 740-765 CE

Sulfate concentration and triple sulfur isotope (32S, 33S, 34S) data measured in TUNU2013 ice-core samples and calculated background-corrected isotope composition (Gabriel et al., in review). S-isotope analyses were made on 65 discrete samples (cross-sections of 6 cm2) cut from archived ice-core sections from TUNU2013, including prior background and full acid deposition lasting over 12 years. The sample resolution over the entire acid deposition event is 3 cm corresponding to a nominal 3-to-4-month age resolution. Sulfate concentration was measured by ion chromatography on the discrete samples, and the sulfate was purified from the melted ice using anion exchange columns. Triple sulfur isotopes (32S, 33S, and 34S) were measured on the samples using a Neptune Plus multi-collector inductively-coupled mass spectrometer (MC-ICP-MS) at the St Andrews Isotope Geochemistry Lab (STAiG lab) (Burke et al., 2019; Burke et al., 2023) and are reported as δ34S and D33S relative to Vienna-Canyon Diablo Troilite (V-CDT), where δxS =(xS/32S)sample/(xS/32S)V-CDT−1. A sample is considered to have a mass-independent fractionation signature if it has a nonzero value of D33S = δ33S -((δ34S + 1)^0.515 − 1), outside of 2σ uncertainty. Full procedural blanks and an in-house secondary standard (Switzer Falls) were processed alongside samples. All data was blank corrected for the process blanks, and uncertainties were propagated with Monte Carlo simulations. The isotopic composition of the volcanic sulfate (δ34Svolc and D33Svolc) was calculated using isotope mass balance and the concentration and isotopic composition of background ice from TUNU2013 taken prior and after the volcanic peaks in sulfate. Data is shown on the NS1-2011 chronology (Sigl et al., 2015). Isotopic composition of the volcanic sulfate is only provided for samples with more than 65% volcanic sulfate following Burke et al. (2019).