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New insights into the ~74 ka Toba eruption from sulfur isotopes of polar ice cores
Climate of the Past ( IF 4.3 ) Pub Date : 2021-04-14 , DOI: 10.5194/cp-2021-38
Laura Crick , Andrea Burke , William Hutchison , Mika Kohno , Kathryn A. Moore , Joel Savarino , Emily A. Doyle , Sue Mahony , Sepp Kipfstuhl , James W. B. Rae , Robert C. J. Steele , R. Stephen J. Sparks , Eric W. Wolff

Abstract. The ~74 ka Toba eruption was one of the largest volcanic events of the Quaternary. There is much interest in determining the impact of such a huge event, particularly on the climate and hominid populations at the time. Although the Toba eruption has been identified in both land and marine archives as the Youngest Toba Tuff, its precise place in the ice core record is ambiguous. Multiple volcanic sulfate signals have been identified in both Antarctic and Greenland ice cores within the uncertainty of age estimates as possible events for the Toba eruption. We measure sulfur isotope compositions in Antarctic ice samples at high temporal resolution across 11 of these potential Toba sulfate peaks in two cores to identify candidates with sulfur mass-independent fractionation (S-MIF), indicative of an eruption whose plume reached altitudes at or above the ozone layer in the stratosphere. Using this method, we identify several candidate sulfate peaks that contain stratospheric sulfur. We further narrow down potential candidates based on the isotope signatures by identifying sulfate peaks that are due to a volcanic event at tropical latitudes. In one of these sulfate peaks at 73.67 ka, we find the largest ever reported magnitude of S-MIF in volcanic sulfate in polar ice, with a Δ33S value of −4.75 ‰. As there is a positive correlation between the magnitude of the S-MIF signal recorded in ice cores and eruptive plume height, this could be a likely candidate for the Toba supereruption, with a plume height in excess of 45 km. These results support the 73.7 ± 0.3 ka (1σ) ka Ar/Ar age estimate for the eruption, with ice core ages of our candidates with the largest magnitude S-MIF at 73.67 and 73.74 ka. Finally, since these candidate eruptions occurred on the transition into Greenland Stadial 20, the relative timing suggests that Toba was not the trigger for the large Northern Hemisphere cooling at this time although we cannot rule out an amplifying effect.

中文翻译:

极地冰芯的硫同位素对〜74 ka鸟羽喷发的新见解

摘要。约74 ka的鸟羽火山喷发是第四纪最大的火山事件之一。人们非常有兴趣确定这种大事件的影响,特别是对当时的气候和人类原始种群的影响。尽管在陆地和海洋档案馆中都将鸟羽喷发定为“最年轻的鸟羽凝灰岩”,但它在冰芯记录中的确切位置却模棱两可。在年龄估计的不确定性范围内,南极和格陵兰岛冰芯中都发现了多种硫酸盐信号,这是多巴火山爆发的可能事件。我们在两个岩芯中的11个潜在的多巴硫酸盐峰中,以高时间分辨率测量南极冰样品中的硫同位素组成,以确定具有硫质量无关分馏(S-MIF)的候选物,指示喷发,其羽流达到平流层中臭氧层或以上的高度。使用此方法,我们确定了几个包含平流层硫的候选硫酸盐峰。通过识别由于热带纬度的火山事件引起的硫酸盐峰,我们基于同位素特征进一步缩小了潜在候选物的范围。在73.67 ka的一个硫酸盐峰之一中,我们发现了极冰中火山硫酸盐中S-MIF的最大报道值,其Δ33 S值为-4.75‰。由于冰芯中记录的S-MIF信号的大小与喷出的羽流高度之间存在正相关关系,因此羽流高度超过45 km的多巴喷发可能成为候选方案。这些结果支持了此次喷发的73.7±0.3 ka(1σ)ka Ar / Ar年龄估算,我们的候选S-MIF最大的冰芯年龄为73.67和73.74 ka。最后,由于这些候选火山爆发是在过渡到格陵兰标准球场20时发生的,因此相对时机表明,尽管我们不能排除放大效应,但此时多巴并不是北半球大面积降温的触发因素。
更新日期:2021-04-14
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