The Pliocene (5.3–2.6 Ma), an epoch with periods of climatic warmth and possible analogue for the future, has been well‐characterized globally by marine geochemical proxies. However, far less is known about Pliocene warmth at continental high latitudes, where the greatest impacts of warming are expected. This study seeks to better characterize the Pliocene climate of central Alaska and Yukon based on a reconstruction of the stable hydrogen isotope composition of precipitation relative to modern (ΔδD_precip) preserved in volcanic glass shards, a proxy for mean air temperature. The studied tephras are from a regional suite of outcrops that, when assembled into a composite record of ΔδD_precip, can be used to resolve broad trends during the late Miocene (6.7–5.86 Ma, n = 5), Pliocene (5.08–2.81 Ma, n = 7), and late Pleistocene (0.74–0.03 Ma, n = 3). These trends indicate that Pliocene ΔδD_precip estimates were generally more enriched in heavy isotopes than the latest Miocene, Pleistocene, and modern intervals. ΔδD_precip is likely influenced by changes in regional boundary conditions including orographic barriers, depositional environments, and ocean‐atmospheric circulation, but ΔδD_precip trends are most consistent with reconstructed temperatures from Yukon‐Alaska and North Pacific marine records. As such, this record appears predominantly sensitive to regional climate. Furthermore, qualitative temperature inferences from branched‐chain glycerol dialkyl glycerol tetraethers (brGDGTs) from four of our sites dating between 2.91 and 6.17 Ma corroborate elevated temperatures during the early Pliocene. Overall, this study demonstrates the viability of volcanic glass δD as a proxy for ΔδD_precip and late Cenozoic climate change in this region.

中文翻译：

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从阿拉斯加中部和育空地区的水合火山玻璃碎片和生物标记物对降水同位素和气候的中新世晚期至更新世晚期重建

上新世（5.3–2.6 Ma）是一个气候温暖时期的时期，可能是未来的类似时期，海洋地球化学代理已经在全球范围内很好地表征了上新世。然而，人们对大陆高纬度的上新世温暖知之甚少，那里预计会出现最大的变暖影响。这项研究旨在通过重建相对于保存在火山玻璃碎片中的现代大气（_ΔδDprecip）的稳定氢同位素组成（相对于平均气温的代表），更好地表征阿拉斯加中部和育空地区的上新世气候。所研究的特弗拉斯来自一套区域露头，当组合成ΔδD_降水的复合记录时，可用于解决中新世晚期（6.7-5.86 Ma，n = 5），上新世（5.08–2.81 Ma，n  = 7）和晚更新世（0.74–0.03 Ma，n  = 3）。这些趋势表明，与最新的中新世，更新世和现代间隔相比，上新世ΔδD_降水估算通常在重同位素中更为丰富。ΔδD_降水可能受区域边界条件变化的影响，包括地形障碍，沉积环境和海洋-大气环流，但ΔδD_降水趋势与育空地区-阿拉斯加和北太平洋海洋记录的重建温度最一致。因此，该记录似乎主要对区域气候敏感。此外，来自我们四个站点的分支链甘油二烷基甘油四醚（brGDGTs）的定性温度推论证实了上新世初期温度升高，该站点的时间为2.91至6.17 Ma。总体而言，这项研究证明了火山玻璃δD可以替代该地区ΔδD_降水和新生代晚期气候变化。