ABSTRACT: Drought can affect even humid regions like northeastern North America, which experienced significant, well-documented dry spells in the 1930s, 50s, 60s, and 80s, and proxies tell us that in the years before instrumentally recorded climate, droughts could be even more severe. To get a more complete picture of pre-recorded climate, the spatial coverage of proxy-based climate reconstructions must be extended. This can better put in context past, current, and future climate, and it can lend anthropological and historical insights. With regard to tree rings as climate proxies, however, there is increasing evidence that relationships between tree growth and climate can be inconsistent over time, in some cases decreasing the utility of tree rings in the representation of climate. We developed a chronology from white cedar Thuja occidentalis tree ring widths for the period 1469-2015 C.E. with which we modeled the relationship between growth and July-September moisture conditions (Palmer Z index). The relationship was consistent across the period of instrumentally recorded climate, 1895-present, and the model explained 27% of variability. Therefore, we used the model to reconstruct July-September moisture conditions from 1546-2014. We found the most variable century to be the 20^th, the least the 18^th. The severest decade-scale droughts (≤0.75 SD from mean) occurred in the 1560s, 1600s/10s, 1630s, 1770s/80s, 1840s, and 1910s/20s, the severest pluvials (≥0.75 SD) in the 1610s/20s, 1660s/70s, and the 1970s/80s. The occasional occurrence of severe droughts throughout the reconstruction, increasing variability in the 20^th century, and expected climate change-enhanced late summer drought, portend a future punctuated with severe droughts.

中文翻译：

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1546年至今，美国密歇根州北部湖面树木重建的夏末潮湿条件

摘要：干旱甚至会影响北美东北部等潮湿地区，在1930年代，50年代，60年代和80年代经历了有据可查的严重干旱，代理人告诉我们，在没有仪器记录在案的气候之前的几年中，干旱甚至可能发生。更严重。为了更全面地了解预先记录的气候，必须扩展基于代理的气候重建的空间覆盖范围。这可以更好地考虑过去，当前和将来的气候，并可以提供人类学和历史的见解。然而，关于树木年轮作为气候代理，越来越多的证据表明，树木的生长与气候之间的关系会随着时间的推移而变得不一致，在某些情况下会降低树木年轮在气候表示中的效用。我们用白雪松开发了年表崖柏树木年轮宽度与我们模拟增长和七月至九月的水分条件（帕尔默之间的关系的时期1469年至2015年CE ž指数）。在仪器记录的气候时期（1895年至今），这种关系是一致的，该模型解释了27％的变异性。因此，我们使用该模型重建了1546-2014年7月至9月的水分状况。我们发现最变量世纪是20^次，最少18^次。十年中最严重的干旱（均值≤0.75 SD）发生在1560s，1600s / 10s，1630s，1770s / 80s，1840s和1910s / 20s，最严重的干旱地区（≥0.75SD）出现在1610s / 20s，1660s / 70年代和1970年代/ 80年代。整个重建严重干旱，偶尔会发生，在20增加变性^个世纪，和预期的气候变化，增强夏末的干旱，预示着严重的干旱打断未来。