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Smoking guns and volcanic ash: the importance of sparse tephras in Greenland ice cores
Polar Research ( IF 1.9 ) Pub Date : 2020-06-08 , DOI: 10.33265/polar.v39.3511
Gill Plunkett , Michael Sigl , Jonathan R. Pilcher , Joseph R. McConnell , Nathan Chellman , J.P. Steffensen , Ulf Büntgen

Volcanic ash (fine-grained tephra) within Greenland ice cores can complement the understanding of past volcanism and its environmental and societal impacts. The presence of ash in sparse concentrations in the ice raises questions about whether such material represents primary ashfall in Greenland or resuspended (remobilized) material from continental areas. In this article, we investigate this issue by examining tephra content in quasi-annual samples from two Greenland ice cores during a period of ca. 20 years and considering their relationships with sulphur and particulate data from the same cores. We focus on the interval 815–835 CE as it encompasses a phase (818–822 CE) of heightened volcanogenic sulphur previously ascribed to an eruption of Katla, Iceland. We find that tephra is a frequent but not continuous feature within the ice, unlike similarly sized particulate matter. A solitary ash shard whose major element geochemistry is consistent with Katla corroborates the attribution of the 822±1 CE sulphur peak to this source, clearly showing that a single shard can signify primary ashfall. Other tephras are present in similarly low abundances, but their geochemistries are less certainly attributable to specific sources. Although these tephra shards tend to coincide with elevated sulphur and fine ( 10 µm) particle concentrations that might be expected if the shards had been transported by dust storms. We conclude that the sparse shards derive from primary ashfall, and we argue that low tephra concentrations should not be dismissed as insignificant.

中文翻译:

吸烟枪和火山灰:格陵兰冰芯中稀疏的火山灰的重要性

格陵兰冰芯中的火山灰(细粒火山灰)可以补充对过去火山活动及其环境和社会影响的理解。冰中稀少浓度的灰烬的存在引发了关于此类物质是否代表格陵兰岛的主要灰烬或来自大陆地区的重新悬浮(再动员)物质的问题。在这篇文章中,我们通过检查来自两个格陵兰冰芯的半年样本中的火山灰含量来研究这个问题。20 年,并考虑它们与来自同一岩心的硫和颗粒数据的关系。我们关注公元 815-835 年的区间,因为它包含一个阶段(公元 818-822 年),以前归因于冰岛卡特拉火山喷发的火山硫升高。我们发现 tephra 是冰中频繁但不连续的特征,与类似大小的颗粒物不同。一个主要元素地球化学与 Katla 一致的孤立灰分碎片证实了 822±1 CE 硫峰对这个来源的归属,清楚地表明单个碎片可以表示初级灰烬。其他 tephras 也以类似的低丰度存在,但它们的地球化学不太确定可归因于特定来源。尽管这些火山灰碎片往往与硫和细颗粒 (10 µm) 浓度升高相吻合,如果碎片是由沙尘暴传播的,则可能会出现这种情况。我们得出的结论是,稀疏的碎片来自原始灰烬,我们认为不应将低火山灰浓度视为微不足道。主要元素地球化学与 Katla 一致的孤立灰分碎片证实了 822±1 CE 硫峰归属于该来源,清楚地表明单个碎片可以表示原始灰烬。其他 tephras 也以类似的低丰度存在,但它们的地球化学不太确定可归因于特定来源。尽管这些火山灰碎片往往与硫和细颗粒 (10 µm) 浓度升高相吻合,如果碎片是由沙尘暴传播的,则可能会出现这种情况。我们得出的结论是,稀疏的碎片来自原始灰烬,我们认为不应将低火山灰浓度视为微不足道。主要元素地球化学与 Katla 一致的孤立灰分碎片证实了 822±1 CE 硫峰归属于该来源,清楚地表明单个碎片可以表示原始灰烬。其他 tephras 也以类似的低丰度存在,但它们的地球化学不太确定可归因于特定来源。尽管这些火山灰碎片往往与硫和细颗粒 (10 µm) 浓度升高相吻合,如果碎片是由沙尘暴传播的,则可能会出现这种情况。我们得出的结论是,稀疏的碎片来自原始灰烬,我们认为不应将低火山灰浓度视为微不足道。但它们的地球化学不太确定可归因于特定来源。尽管这些火山灰碎片往往与硫和细颗粒 (10 µm) 浓度升高相吻合,如果碎片是由沙尘暴传播的,则可能会出现这种情况。我们得出的结论是,稀疏的碎片来自原始灰烬,我们认为不应将低火山灰浓度视为微不足道。但它们的地球化学不太确定可归因于特定来源。尽管这些火山灰碎片往往与硫和细颗粒 (10 µm) 浓度升高相吻合,如果碎片是由沙尘暴传播的,则可能会出现这种情况。我们得出的结论是,稀疏的碎片来自原始灰烬,我们认为不应将低火山灰浓度视为微不足道。
更新日期:2020-06-08
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