Evaluating the timing and structure of the 4.2 ka event in the Indian summer monsoon domain from an annually resolved speleothem record from Northeast India
Evaluating the timing and structure of the 4.2 ka event in the Indian summer monsoon domain from an annually resolved speleothem record from Northeast India
复制标题
根据印度东北部每年解析的洞穴记录评估印度夏季季风域 4.2ka 事件的时间和结构
DOI：
10.5194/cp-14-1869-2018
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发表时间：
2018-11-30
影响因子：
4.3
通讯作者：
Edwards, R. Lawrence
中科院分区：
文献类型：
--
作者：
Kathayat, Gayatri;Cheng, Hai;Edwards, R. Lawrence
大量的代用记录表明，“4.2 ka事件”标志着大约300年（类似于3.9至4.2 ka）的主要气候变化的地球仪。然而，这一事件的气候表现，包括其开始，持续时间和终止，仍然不太清楚，在印度夏季风（ISM）域。在这里，我们提出了新的氧同位素（δ O-18）数据从一对洞穴（ML.1和ML.2）Mawmluh洞，梅加拉亚，印度，提供了一个高分辨率的记录ISM的变化在一个时期（类似于3.78和4.44万年），完全涵盖了4.2万年的事件。次年度到年度解决ML.1三角洲O-18记录的限制，18 Th-230日期的平均测年误差为+/- 13年（2西格玛）和分辨率类似于40年，这使我们能够表征ISM的变化与前所未有的细节。在与4.2 ka事件同期的ISM变化的推断模式与以前的重建从Mawmluh洞穴和该地区的其他代理记录的ISM共享广泛的相似性和关键的差异。我们的数据表明，ISM强度，在我们的记录的长度的背景下，突然下降，在类似于4.0 ka（类似于+/- 13年），标志着一个多世纪的相对减少ISM，这是由至少两个几十年的干旱类似于3.9和4.0 ka之间的开始。后者与ISM的一些先前的代理重建形成鲜明对比，其中4.2 ka事件被描述为一个单一的数百年干旱。
A large array of proxy records suggests that the "4.2 ka event" marks an approximately 300-year long period (similar to 3.9 to 4.2 ka) of major climate change across the globe. However, the climatic manifestation of this event, including its onset, duration, and termination, remains less clear in the Indian summer monsoon (ISM) domain. Here, we present new oxygen isotope (delta O-18) data from a pair of speleothems (ML.1 and ML.2) from Mawmluh Cave, Meghalaya, India, that provide a high-resolution record of ISM variability during a period (similar to 3.78 and 4.44 ka) that fully encompasses the 4.2 ka event. The sub-annually to annually resolved ML.1 delta O-18 record is constrained by 18 Th-230 dates with an average dating error of +/- 13 years (2 sigma) and a resolution of similar to 40 years, which allows us to characterize the ISM variability with unprecedented detail. The inferred pattern of ISM variability during the period contemporaneous with the 4.2 ka event shares broad similarities and key differences with the previous reconstructions of ISM from the Mawmluh Cave and other proxy records from the region. Our data suggest that the ISM intensity, in the context of the length of our record, abruptly decreased at similar to 4.0 ka (similar to +/- 13 years), marking the onset of a multi-centennial period of relatively reduced ISM, which was punctuated by at least two multi-decadal droughts between similar to 3.9 and 4.0 ka. The latter stands out in contrast with some previous proxy reconstructions of the ISM, in which the 4.2 ka event has been depicted as a singular multi-centennial drought.