Abstract Sediment in lakes and meadows forms a powerful archive that can be used to reconstruct environmental change through time. Reconstructions of lake level, of chemical, biological, and hydrological conditions, and of surrounding vegetation provide detailed information about past climate conditions, both locally and regionally. Indeed, most of our current knowledge of centennial- to millennial-scale climate variability in the arid western United States, where information about past hydroclimate is particularly important, comes from such sediment-based reconstructions. The pressing need for robust, precise predictions of future conditions is a significant motivation for paleoclimate science, and current research questions frequently require Holocene reconstructions to be resolved at sub-centennial timescales. Increasingly, regional syntheses seek to identify synoptic-scale patterns similar to those defined from modern observations (seasonal, interannual, multi-decadal, etc.) or to compare with the output of climate model simulations. However, the age control on existing records, especially those more than about 20 years old, is often sufficient only for millennial-scale interpretation. Here we assess the age control for 84 published and unpublished records from lakes and meadows in the Great Basin, California, and desert southwest, and use Bayesian modeling to evaluate the 95% uncertainty ranges for the 42 best-dated records. In the Late Holocene, about half of the 42 records have 800-year mean uncertainty and records of the Early Holocene have 600- to >1400-year mean uncertainty ranges. We find that the largest control on modeled uncertainties is dating density, with at least 2 dates/kyr being optimal and suggest obtaining “range-finder” dates at the onset of a study to better predict the total number of dates needed for an adequate age model. Such a density avoids a commonly observed phenomenon of significant peaks in uncertainty arising in gaps between age control points. Analysis of the uncertainties associated with proxy shifts reveal that more than half are >400 years. Although such large uncertainties currently prevent sub-centennial interpretations in most cases, increased dating density, strategic use of limited funds (including budgeting for a 2 date/kyr minimum at the proposal stage), construction of age-depth models with Bayesian methods, and critical evaluation of chronological uncertainty will shed light on past climate variability at finer timescales, enhancing our understanding of global and regional drivers of western U.S. climate.

中文翻译：

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美国西部全新世古气候变化：年代学在辨别模式和驱动因素中的重要性

摘要 湖泊和草地中的沉积物形成了一个强大的档案，可用于重建环境随时间的变化。湖泊水位、化学、生物和水文条件以及周围植被的重建提供了当地和区域过去气候条件的详细信息。事实上，我们目前对美国西部干旱地区百年至千禧年气候变化的大部分了解都来自于这种基于沉积物的重建，那里的过去水文气候信息尤为重要。迫切需要对未来条件进行可靠、精确的预测，这是古气候科学的一个重要动力，当前的研究问题经常需要在亚百年的时间尺度内解决全新世重建问题。日益，区域综合力求确定类似于现代观测（季节性、年际、多年代际等）定义的天气尺度模式，或与气候模式模拟的输出进行比较。然而，对现有记录的年龄控制，尤其是那些超过 20 年的记录，通常仅适用于千禧年尺度的解释。在这里，我们评估了来自加利福尼亚大盆地和西南沙漠的湖泊和草地的 84 条已发表和未发表记录的年龄控制，并使用贝叶斯模型来评估 42 条最佳日期记录的 95% 不确定性范围。在全新世晚期，42 条记录中约有一半具有 800 年的平均不确定性，而全新世早期的记录具有 600 至 >1400 年的平均不确定性范围。我们发现对建模不确定性的最大控制是测年密度，至少 2 个日期/kyr 是最佳的，并建议在研究开始时获取“测距仪”日期，以更好地预测适当年龄模型所需的日期总数。这种密度避免了在年龄控制点之间的间隙中出现的不确定性显着峰值的常见现象。与代理变化相关的不确定性分析表明，超过一半的时间超过 400 年。尽管目前在大多数情况下如此大的不确定性阻止了对次百年的解释，但增加了年代密度，战略性地使用了有限的资金（包括在提案阶段为 2 个日期 / kyr 最低预算），使用贝叶斯方法构建年龄深度模型，以及对时间顺序不确定性的批判性评估将在更精细的时间尺度上揭示过去的气候变化，