The arid southwestern United States is susceptible to sustained droughts that impact water resources and economic activity for millions of residents. Previous work has not systematically investigated the structure, timing, and possible forcings of Holocene Great Basin sub‐orbital hydroclimate changes, impeding our ability to understand the potential future controls on Southwestern aridity. The objective of this paper is to constrain the potential forcings on Holocene aridity and temperature, via comparison of new high‐resolution speleothem data, an Aridity Index synthesizing hydroclimate records, and linkages of Southwestern paleoclimate to other regions. The high‐resolution data from Leviathan Cave provide a paleoclimate record since 13,400 yr ago: A cool Younger Dryas was followed by two pronounced Middle Holocene aridity intervals between 9,850 and 5,310 yr B2k characterized by low growth rates and high δ¹⁸O and δ¹³C values. Subsequently, stalagmite δ¹⁸O values show near‐modern levels for the last four millennia during which time growth rates were high and δ¹³C values were low in response to wetter conditions. The regional Aridity Index documents that Middle Holocene drying coincided with a warm Arctic and decreased sea ice extent, a warm western tropical Pacific, and a large sea surface temperature gradient across the tropical Pacific, all of which likely responded to northern hemisphere summer insolation forcing. Our data suggest that extreme Middle Holocene aridity is more severe than the short medieval droughts evident in the tree ring record, and such extreme aridity may represent a worst‐case analog for future climate.

中文翻译：

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大盆地的古气候和干旱与北极变暖和热带太平洋海表温度有关

美国西南干旱地区易受持续干旱的影响，干旱影响数百万居民的水资源和经济活动。先前的工作尚未系统地研究全新世大盆地亚轨道水文气候变化的结构，时间和可能的强迫，这阻碍了我们了解西南干旱未来潜在控制的能力。本文的目的是通过比较新的高分辨率脾脏数据，合成水文气候记录的干旱指数以及西南古气候与其他地区的联系，来限制全新世干旱和温度的潜在强迫。来自Leviathan Cave的高分辨率数据提供了自13,400年前的古气候记录：凉爽的Younger Dryas之后是两个全新世的干旱全新世，间隔为9，¹⁸ O和δ ^13个C值。随后，石笋δ ^18个O值显示近现代水平在过去的四个千年，在此期间的增长率很高，δ ^13个C值响应潮湿条件低。区域干旱指数表明，全新世中期干燥与北极温暖和海冰范围减少，热带热带太平洋西部暖化以及整个热带太平洋海面温度梯度大有关，所有这些都可能响应了北半球夏季的日照强迫。我们的数据表明，中新世极端干旱比树环记录中所示的中世纪短时干旱更为严重，而这种极端干旱可能代表了未来气候的最坏情况。