Millennial- and centennial-scale droughts at the northern margin of the East Asian summer monsoon during the last deglaciation: Sedimentological evidence from Dali Lake
Millennial- and centennial-scale droughts at the northern margin of the East Asian summer monsoon during the last deglaciation: Sedimentological evidence from Dali Lake
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末次冰消期东亚夏季风北缘千年百年尺度干旱：来自达里湖的沉积学证据
DOI：
10.1016/j.palaeo.2018.11.001
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Qin Xiaoguang
中科院分区：
文献类型：
--
作者：
Fan Jiawei;Xiao Jule;Qin Xiaoguang
近几十年来，东亚夏季风(EASM)北缘的半干旱地区经历了更频繁的干旱。然而，目前尚不清楚该地区过去的季风降水主要是由厄尔尼诺-南方涛动(ENSO)变化还是高纬度冷却决定的。在这项研究中，我们使用一个高分辨率的粒度数据集，结合一个新的贝叶斯年龄深度模型，分析了在末次冰川消融期间气候变暖期间，EASM边缘发生的千年和百年尺度的干旱。采用对数正态分布函数拟合法对多峰粒度分布进行了划分。粗组分(C4+C5+C6)的高百分比被认为是强风沙活动和低湖水位的替代指标，因此该地区发生了干旱。在千年和百年时间尺度上，干旱事件通常伴随着区域温度、集水区地表径流和生物生产力的下降。这些结果表明，东亚夏季风边缘的干旱是由东亚夏季风强度显著减弱引起的。此外，在年龄不确定的情况下，干旱可能与千年时间尺度上的Heinrich 1(H1)和Young Dryas(YD)事件有关，以及与百年时间尺度上较老的Dryas(OD)冷事件有关，这意味着强烈的高纬度强迫。考虑到北部高纬度地区的这些冷逆转是由于上一次冰川消融期间冰川融水迅速输入北大西洋造成的，因此持续的气候变暖以及由此导致的北纬高纬度冰盖融化可能会导致中国北部干旱的发生率增加。
The semi-arid areas at the northern margin of the East Asian summer monsoon (EASM) have experienced an increased frequency of drought in recent decades. However, it is unclear whether past monsoonal precipitation in the region were determined mainly by El Niño-Southern Oscillation (ENSO) variability or high-latitude cooling. In this study, we use a high-resolution grain-size dataset combined with a new Bayesian age–depth model of a sediment core from Dali Lake to analyze the occurrence of millennial- and centennial-scale droughts at the EASM margin during the interval of climatic warming during the last deglaciation. The polymodal grain-size distributions are partitioned using a log-normal distribution function fitting method. High percentages of the coarse components (C4+C5+C6) are recognized as proxy indicators of strong aeolian activities and low lake levels, and thus droughts in the region. The drought events indicated thereby are generally accompanied by decreases in regional temperature, catchment surface runoff and bio-productivity, on both millennial and centennial timescales. These results imply that the droughts at the EASM margin were caused by a significantly weakened EASM intensity. In addition, the droughts may be linked, within the age uncertainties, to the Heinrich 1 (H1) and Younger Dryas (YD) events on millennial timescales, and to the Older Dryas (OD) cold event on centennial timescales, implying strong high-latitude forcing. Given that these cold reversals over northern high latitudes were induced by the rapid input of glacial melt-water to the North Atlantic during the last deglaciation, it is possible that ongoing climatic warming, and the resulting high northern-latitude ice-sheet melting, may cause an increased incidence of drought in northern China.