Sulfur isotopes of sulfate measurements from a Greenland ice core (1850-2006)

Anthropogenic sulfate aerosols are estimated to have offset sixty percent of greenhouse-gas-induced warming in the Arctic, a region warming four times faster than the rest of the world. However, sulfate radiative forcing estimates remain uncertain because the relative contributions from anthropogenic versus natural sources to total sulfate aerosols are unknown. Here we measure sulfur isotopes of sulfate in a Summit, Greenland ice core from 1850 to 2006 CE to quantify the contribution of anthropogenic sulfur emissions to ice core sulfate. We use a Keeling Plot to determine the anthropogenic sulfur isotopic signature (δ34Santhro = +2.9  0.3 ‰), and compare this result to a compilation of sulfur isotope measurements of oil and coal. Using δ34Santhro, we quantify anthropogenic sulfate concentration separated from natural sulfate. Anthropogenic sulfate concentration increases to 68 ± 7% of non-sea-salt sulfate (65.1 ± 20.2 µg kg-1) during peak anthropogenic emissions from 1960 to 1990 and decreases to 45 ± 11% of non-sea-salt sulfate (25.4 ± 12.8 µg kg-1) from 1996 to 2006. These observations provide the first long-term record of anthropogenic sulfate distinguished from natural sources (e.g., volcanoes, dimethyl sulfide), and can be used to evaluate model characterization of anthropogenic sulfate aerosol fraction and radiative forcing over the industrial era. These data include sulfur isotopes of sulfate measurements from a Greenland ice core from 1850-2006. The preindustrial dataset (1200-1850) is uploaded to the Arctic data center here: doi:10.18739/A2N873162

人为硫酸盐气溶胶（Anthropogenic sulfate aerosols）经估算可抵消北极地区60%的温室气体引发的增温效应——该区域的变暖速率是全球其他区域的4倍。然而，硫酸盐辐射强迫（radiative forcing）的估算仍存在不确定性，因人为源与自然源对总硫酸盐气溶胶的相对贡献尚不明确。本研究通过测定公元1850年至2006年格陵兰萨米特冰芯中的硫酸盐硫同位素，量化人为硫排放对冰芯硫酸盐的贡献。我们采用基林图（Keeling Plot）确定了人为硫的同位素特征（δ³⁴S_anthro = +2.9 ± 0.3 ‰），并将该结果与石油、煤炭的硫同位素测量汇编数据进行对比。依托该人为硫同位素特征，我们分离并定量了人为硫酸盐与自然硫酸盐的浓度：在1960年至1990年的人为排放峰值期，人为硫酸盐占非海盐硫酸盐的比例升至68 ± 7%（浓度为65.1 ± 20.2 µg kg⁻¹）；1996年至2006年，该比例下降至45 ± 11%（浓度为25.4 ± 12.8 µg kg⁻¹）。本观测结果首次提供了可区分自然源（如火山、二甲基硫（dimethyl sulfide））与人为源的硫酸盐长期记录，可用于评估工业时代人为硫酸盐气溶胶占比及辐射强迫的模型表征能力。本数据集包含1850年至2006年格陵兰冰芯的硫酸盐硫同位素测量数据。公元1200年至1850年的前工业化数据集已上传至北极数据中心，链接为：doi:10.18739/A2N873162