Assessing the strength of the monsoon during the late Pleistocene in southwestern United States
Assessing the strength of the monsoon during the late Pleistocene in southwestern United States
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评估美国西南部更新世晚期季风的强度
DOI：
10.1016/j.quascirev.2014.08.022
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发表时间：
2014
影响因子：
4
通讯作者：
M. Berke
中科院分区：
文献类型：
--
作者：
L. Cisneros;Yongsong Huang;J. Heikoop;P. Fawcett;J. Fessenden;R. Anderson;P. Meyers;T. Larson;G. Perkins;J. Toney;J. Werne;F. Goff;G. Woldegabriel;C. Allen;M. Berke
改进对干旱的预测需要了解自然和人为引起的气候变化。跨越冰期-间冰期旋回的长期记录提供了变率的自然成分，但美国西南部的此类记录很少，降水的定量或半定量记录也缺失。本文利用更新世湖相沉积物中c28n -烷酸的氢同位素（δD）值重建了新墨西哥北部两个冰期-间冰期旋回（距今约55万年至36万年）降水的δD值，并获得了季风强度的记录。总体而言，重建δD值范围为- 53.8‰~ - 94.4‰，平均值为- 77.5±8‰。值得注意的是，这一变化落在现今夏季季风和冬季加权平均值（分别为- 50.3±3‰和- 106.4±20‰）之内，表明在海洋同位素阶段（MIS） 13至10期间，与当前过程相似的过程也控制了降水。利用夏季季风和冬季的δD平均值作为端元，我们将重建的降水δD记录解释为MIS 13至10期间季风强度的直接和半定量指标。间冰期的特点是季风强度更大，但与冰期相比变化也更大。季风强度的明显周期发生在间冰期，总体上与年最高平均气温呈正相关。我们对季风强度的估计得到了生态系统生产力的独立代用指标，即TOC、TOC δ13C和Si/Ti比值以及暖花粉类群杜松和栎的支持。间冰期季风强度的变化类似于对陆海表面温度对比（LSTC）的响应，除了MIS 11的早期部分。在此期间，LSTC将保持相对强劲，而季风强度则降至最低。这个最小值出现在MIS 11最温暖的间隔之后，表明在温暖期季风强度的驱动更为复杂。此外，季风极小期与泥裂沉积物的核心部分相吻合，这表明季风降水减少是干旱发生的重要因素。我们对季风强度的估计代表了该地区与现在有关的自然变率的记录，特别是间冰期MIS 11的变率，它被认为是当前间冰期的模拟。我们的研究结果表明，自然变率可以导致季风降水的显著减少，这意味着持续变暖的潜在不利影响。
Improved predictions of drought require an understanding of natural and human-induced climate variability. Long-term records across glacial–interglacial cycles provide the natural component of variability, however few such records exist for the southwestern United States (US) and quantitative or semi-quantitative records of precipitation are absent. Here we use the hydrogen isotope (δD) value of C28n-alkanoic acid in lacustrine sediments of Pleistocene age to reconstruct δD values of precipitation in northern New Mexico over two glacial–interglacial cycles (∼550,000–360,000 years before present) and obtain a record of monsoon strength. Overall, reconstructed δD values range from −53.8‰ to −94.4‰, with a mean value of −77.5 ± 8‰. Remarkably, this variation falls within the measured present-day summer monsoonal and winter weighted means (−50.3 ± 3‰ and −106.4 ± 20‰ respectively), suggesting that processes similar to those of present time also controlled precipitation during Marine Isotope Stage (MIS) 13 to 10. Using the δD summer monsoonal and winter mean values as end-members, we interpret our reconstructed δD record of precipitation as a direct, and semi-quantitative, indicator of monsoon strength during MIS 13 to 10. Interglacial periods were characterized by greater monsoon strength but also greater variability compared to glacial periods. Pronounced cycles in the strength of the monsoon occurred during interglacial periods and in general were positively correlated with maximum mean annual temperatures. Our estimates of monsoon strength are supported by independent proxies of ecosystem productivity, namely, TOC, δ13C of TOC and Si/Ti ratio and warm pollen taxaJuniperusandQuercus. Interglacial variability in the strength of the monsoon resembles a response to the land-sea surface temperature contrast (LSTC) except for the early part of MIS 11. During this period, LSTC would have remained relatively strong while monsoonal strength decreased to a minimum. This minimum occurred following the warmest interval of MIS 11, suggesting a more complex driving of monsoon strength during warm periods. In addition, this period of monsoon minimum coincided with a core section of mud-cracked sediments that suggest low monsoonal precipitation was an important factor in the onset of drought. Our estimates of monsoon strength represent a record of natural variability in the region that is relevant to present time, in particular the variability during interglacial MIS 11, which is considered an analog for the current interglacial. Our results suggest that natural variability can cause significant reductions in monsoonal precipitation with the implication of a potentially adverse effect from sustained warming.
影响因子：
5
作者：
D. Sachse;J. Radke;G. Gleixner
通讯作者：
D. Sachse;J. Radke;G. Gleixner
陆地植物中各个正构烷烃沿气候梯度的 ΔD 值 â 对沉积生物标志物记录的影响
影响因子：
3
作者：
Sachse;Gleixner
通讯作者：
Gleixner