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Greater drought intensity and frequency before AD 1200 in the Northern Great Plains, USA

机译：美国北部大平原在公元1200年之前的干旱强度和频率更高

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摘要

EXTREME large-scale droughts in North America, such as the 'Dust Bowl' of the 1930s, have been infrequent events within the documented history of the past few hundred ycars, yet this record may not be representative of long-term patterns of .natural variation of drought intensity and frequency. In the Great Plains region of central North America, historical droughts have persisted longer than in any other part of the United States', hut no detailed records of drought patterns in this region have hitherto been obtained that extend beyond the past 500 years. Here we present a reconstruction of drought intensity and frequency over the past 2,300 years in the Northern Great Plains, based on lake salinity fluctuations inferred from fossil diatom assemblages. This record, of sub-decadal resolution, suggests that extreme droughts of greater intensity than that of the 1930s were more frequent before AD 1200. This high frequency of extreme droughts persisted for centuries, and was most pronounced during AD200-370, AD 700-850 and Ad lOOOr-1200. We suggest that before AD 1200, the atmospheric circulation anomalies that produce drought today were more frequent and persistent.
机译：在过去的几百辆ycar记录的历史中，北美极度大规模的干旱，例如1930年代的“沙尘碗”，已经很少发生，但该记录可能并不代表.natural的长期模式。干旱强度和频率的变化。在北美中部的大平原地区，历史干旱持续的时间比美国其他任何地方都长，但迄今为止，尚未获得该地区干旱时间超过500年的详细记录。在这里，我们根据化石硅藻组合推断出的盐度波动，提出了大平原北部过去2300年干旱强度和频率的重建。该记录显示的年代际分辨率表明，比1930年代强度更大的极端干旱在公元1200年之前更为频繁。这种极端干旱的频率持续了几个世纪，在AD200-370，AD 700- 850和​​Ad 100Or-1200。我们建议，在公元1200年之前，今天引起干旱的大气环流异常更加频繁和持久。

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