Stratospheric eruptions from tropical and extra-tropical volcanoes constrained using high-resolution sulfur isotopes in ice cores
Stratospheric eruptions from tropical and extra-tropical volcanoes constrained using high-resolution sulfur isotopes in ice cores
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DOI：
10.1016/j.epsl.2019.06.006
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发表时间：
2019-09-01
影响因子：
5.3
通讯作者：
Adkins, Jess F.
中科院分区：
文献类型：
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作者：
Burke, Andrea;Moore, Kathryn A.;Adkins, Jess F.
过去2500年火山对气候的强迫作用主要是基于冰芯中的硫酸盐浓度。特别令人感兴趣的是大型火山爆发，其羽流到达平流层的高空，因为这些使硫酸盐气溶胶在大气中停留时间最长，因此对辐射强迫的影响最大。在冰芯中测量的硫同位素可用于识别这些大喷发，因为平流层硫暴露于紫外线辐射，这赋予了保存在冰中的随时间变化的质量独立分馏（MIF）。然而，传统测量技术的样本量要求意味着MIF信号可能被掩盖，导致不确定的结果。在这里，我们提出了一种新的方法来测量冰芯中的硫同位素的多接收电感耦合等离子体质谱法，它减少了三个数量级的样品量的要求。我们的方法使我们能够测量含硫量低至10 nmol的样品，δ S-34的精度为0.11 ppm，δ S-33的精度为0.10 ppm，从而实现了冰芯硫酸盐峰的高时间分辨率。我们测试了这种方法对已知的热带（Tambora 1815和Samalas 1257）和热带外（Katmai/Novarupta 1912）平流层喷发从Tunu 2013冰芯在格陵兰岛和B40冰芯从南极洲。这些高分辨率的硫同位素记录表明，热带与热带外火山爆发的特征之间存在明显差异。此外，同位素质量平衡硫酸盐从热带外喷发提供了一种手段，以估计硫酸盐沉积的分数，来自平流层。这项技术应用于冰芯中未确认的喷发，因此可能会改善火山爆发及其对气候影响的记录。(C)2019爱思唯尔B. V.保留所有权利。
The record of volcanic forcing of climate over the past 2500 years is based primarily on sulfate concentrations in ice cores. Of particular interest are large volcanic eruptions with plumes that reached high altitudes in the stratosphere, as these afford sulfate aerosols the longest residence time in the atmosphere, and thus have the greatest impact on radiative forcing. Sulfur isotopes measured in ice cores can be used to identify these large eruptions because stratospheric sulfur is exposed to UV radiation, which imparts a time-evolving mass independent fractionation (MIF) that is preserved in the ice. However, sample size requirements of traditional measurement techniques mean that the MIF signal may be obscured, leading to an inconclusive result. Here we present a new method of measuring sulfur isotopes in ice cores by multi-collector inductively coupled plasma mass spectrometry, which reduces sample size requirements by three orders of magnitude. Our method allows us to measure samples containing as little as 10 nmol of sulfur, with a precision of 0.11 parts per thousand for delta S-34 and 0.10 parts per thousand for Delta S-33, enabling a high-temporal resolution over ice core sulfate peaks. We tested this method on known tropical (Tambora 1815 and Samalas 1257) and extra-tropical (Katmai/Novarupta 1912) stratospheric eruptions from the Tunu2013 ice core in Greenland and the B40 ice core from Antarctica. These high-resolution sulfur isotope records suggest a distinct difference between the signatures of tropical versus extra-tropical eruptions. Furthermore, isotope mass balance on sulfate from extra-tropical eruptions provides a means to estimate the fraction of sulfate deposited that was derived from the stratosphere. This technique applied to unidentified eruptions in ice cores may thus improve the record of explosive volcanism and its forcing of climate. (C) 2019 Elsevier B.V. All rights reserved.