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>A Tale of Three Sisters: Reconstructing the Holocene glacial history and paleoclimate record at Three Sisters Volcanoes, Oregon, United States
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A Tale of Three Sisters: Reconstructing the Holocene glacial history and paleoclimate record at Three Sisters Volcanoes, Oregon, United States
At least four glacial stands occurred since 6.5 ka B.P. based on moraines located on the eastern flanks of the Three Sisters Volcanoes and the northern flanks of Broken Top Mountain in the Central Oregon Cascades. The youngest of these advances was the Little Ice Age (LIA) glaciation, which reached its maximum advance 150-200 yrs. B.P. and is defined by the large sharp crested and unvegetated moraines adjacent to the modern glaciers. In isolated locations less than 100 m downslope from these moraines, a second set of sparsely vegetated lateral moraines marks the Late-Neoglacial stand of the glaciers between 2.1 ± 0.4 and 7.7 ka B.P, A third set of Early-Neoglacial end moraines is 300-700 meters downslope of the modern glacier termini, and postdates 7.7 ka B.P. From SST temperature data (Barron et al., 2003) and a speleothem record (Vacco, 2003), we infer that this advance occurred between 4.5 and 6.5 ka B.P. Finally, the Fountonnor stand is marked by moraines 500-900 meters downslope of the modern glacier termini, and we infer these are latest Pleistocene or early Holocene.Modem equilibrium line altitudes (ELAs) at the Three Sisters and Broken Top are approximately 2500 - 2600 m. During the LIA, the ELAs were 40 - 180 m lower, requiring cooler mean summer temperatures by 0.7 - 1.0°C and winter snowfall to increase by 10 - 60 cm water equivalent. The average Early Neoglacial and Fountonnor ELAs were 130 - 300 m and 290 - 320 m lower than modem glaciers, respectively, requiring air temperatures to be 0.7 - 1.6°C and 1.5 - 1.7°C cooler during the summer and winter snowfall to be 40 - 100 cm water equivalent and 90 - 100 cm water equivalent greater.
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机译：自6.5 ka B.P.起至少发生了4个冰期。基于位于三姐妹火山东侧和俄勒冈州中部小瀑布的断顶山北侧的冰rain。这些进展中最年轻的是小冰河时代（LIA）的冰期，达到了150-200年的最大进展。 B.P.由与现代冰川相邻的大型尖峰和无植被的冰defined定义。在离这些滑坡不到100 m的下坡孤立地带，第二组稀疏的植被侧向滑坡标志着冰川的晚新冰期架势在2.1±0.4和7.7 ka BP之间，第三组早冰期的端部冰原为300-现代冰川终点站的700米下坡，以及7.7 ka BP从SST温度数据（Barron等人，2003）和speleothem记录（Vacco，2003），我们可以推断出这一进展发生在4.5和6.5 ka B.P.之间。最后，Fountonnor站以现代冰川末端500-900米的冰rain下坡为标志，我们推断这是最新的更新世或全新世早期。三姐妹和断顶的现代平衡线高度（ELA）约为2500-2600米在LIA期间，ELA降低了40-180 m，要求夏季平均温度降低0.7-1.0°C，冬季降雪量增加10-60 cm水当量。早期新冰川和Fountonnor ELA的平均水平分别比现代冰川低130-300 m和290-320 m，夏季和冬季的降雪温度分别为0.7-1.6°C和1.5-1.7°C凉爽40 -100厘米水当量和90-100厘米水当量。
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