Rapid, time-transgressive, and variable responses to early Holocene midcontinental drying in North America
Rapid, time-transgressive, and variable responses to early Holocene midcontinental drying in North America
复制标题
对北美全新世早期大陆中部干旱的快速、随时间推移和变化的反应
作者：
John W. Williams;B. Shuman;Patrick J. Bartlein;N. Diffenbaugh;T. Webb,
更新世末至全新世早期北美大陆中部的干旱是了解区域干旱，其驱动因素及其影响的重要案例研究。本文综合花粉，δ 13 C，风成，和古水文代用品记录的空间和时间模式的开始和干燥的速度。发病的时间范围从14至6万年，大多数网站干燥10至8万年（日历年前）。主要的空间格局是时间海侵的，大平原内部遗址先于周边遗址开始干燥。这种时间的海侵趋势可以解释为一个区域范围内的干燥，导致生态交错区向东移动，或可能表明从西向东的大气干燥的逐步转移。三分之一的网站迅速响应干燥，一个集群的快速反应发生约。8 ka。14和6 ka之间的爆发和8 ka时的快速响应相结合，强烈表明：（1）夏季高日照、Laurentide冰盖退缩和阿加西湖排水的组合驱动了中部大陆干燥，（2）干燥加速了Laurentide冰盖在8.4 ka的崩溃。当地因素强烈调解的时间和速度的网站响应区域干燥。地方对大平原未来干旱的反应也应该是高度可变的，这对未来气候变化的影响评估提出了挑战。
The end Pleistocene to early Holocene drying of the North American midcontinent is an important case study for understanding regional drought, its drivers, and its impacts. This paper synthesizes pollen, δ13C, eolian, and paleohydrological proxies to document the spatial and temporal patterns in the onset and rate of drying. The timing of onset ranged from 14 to 6 ka with most sites drying between 10 and 8 ka (calendar years ago). The dominant spatial pattern is time transgressive, with interior Great Plains sites beginning to dry before peripheral sites. This time-transgressive trend can be explained as a region-wide drying that caused ecotones to shift eastward, or could indicate a progressive shift in atmospheric drying from west to east. One-third of sites responded rapidly to drying; a cluster of rapid responses occurred ca. 8 ka. The combination of onsets between 14 and 6 ka and rapid responses at 8 ka strongly suggests that (1) the combination of high summer insolation, Laurentide Ice Sheet retreat, and Lake Agassiz drainage drove midcontinental drying, and (2) drying accelerated with Laurentide Ice Sheet collapse at 8.4 ka. Local factors strongly mediate the timing and rate of site responses to regional drying. Local responses to future drying in the Great Plains also should be highly variable, which challenges impact assessments of future climate changes.