摘要
H2事件是发生于末次冰盛期的一次显著的气候突变事件,对理解千年气候事件和内部机制具有重要意义.然而,目前具有高精度和精确定年的H2事件气候记录依然很少,这在很大程度上限制了对H2事件起止时间、内部细节和触发机制的进一步研究.本研究基于印度东北部乞拉朋齐洞(Cherrapunji Cave)具有年纹层的石笋CHE-2 (总长940 mm)的21个U-Th年代、 2701条纹层的计数和259个δ18O数据,重建了25. 50~24. 76 ka B. P.和24. 38~22. 42 ka B. P.(99. 5~437. 0 mm样品段)期间石笋δ18O的高分辨率(24. 38~23. 08 ka B. P.时段平均分辨率8年,其他时段平均分辨率14年)、精确时间序列,刻画了印度东北部地区H2事件的结束过程和精细结构.研究表明,乞拉朋齐洞石笋记录的H2事件结束时段为 24. 280±0. 028~23. 436±0. 028 ka B. P.,共持续 844±3年,振幅约为1. 9‰,事件发生时间在误差范围内与东亚季风区石笋记录和格陵兰冰芯记录同步,在此期间,δ18O记录呈现了两次负偏过程(24. 28~24. 17 ka B. P.和23. 90~23. 44 ka B. P.)和一段相对稳定过程(24. 17~23. 90 ka B. P.),叠加了多个百年-十年际尺度的气候振荡.本研究得到的高分辨率δ18O精确时间序列对于改善气候模型和检验气候事件假说有一定意义.从亚洲季风区与高纬地区同时段H2事件记录的对比来看,其发生机制可能主要包括以下几个方面: 1)淡水注入北大西洋导致AMOC减弱,北高纬温度降低,推动ITCZ南移;北高纬温度变化的信号通过西风带和蒙古冷高压传递到亚洲季风区,从而影响亚洲夏季风;2)H2事件结束过程可能受到南极缓慢变暖的影响;3)低纬和青藏高原的变化也可能对H2事件产生复杂的影响.这些依然有待更多的高分辨率记录和气候模拟结果的进一步验证.
The Heinrich 2 (H2) Event is among one of the abrupt cold events, which is first recognized from the North Atlantic Ocean as an ice-rafted debris event during the Last Glacial Period. The detailed structure (e.g., timing, duration) under constraint chronology of this millennial scale climatic event can provide a better understanding of the underlying forcing mechanisms. However, up to now, there are only a few high-resolution and precisely-dated paleoclimate records across the H2 Event, which largely impedes our ability to understand its timing, structure and the potential forcing mechanisms. Here, we present a cave speleothem oxygen isotope (δ18O) record (stalagmite CHE-2, total length is 940 mm) from the Cherrapunji Cave (25°11'59"N, 92°27'11"E;1100 m a.s.l.), Northeast India. This record has high resolution (259 oxygen isotope data, an average resolution of 8 years between 24.38 ka B. P.(before present, present=1950 A.D.) to 23.08 ka B. P. and 14 years for other period), and reconstruction of the Indian monsoon during H2 Event is constrained not only by 21 high-precision U-Th ages (average age uncertainty is ±60 years), additionally via annual fluorescent lamination counting (2701 annual bands, further supported by the U-Th ages) using the Laser Scanning Confocal Microscope. The unprecedented δ18O resolution and chronology of our record allow us to characterize in detail the Indian monsoon history from 25.50 ka B. P. to 24.76 ka B. P. and 24.38 ka B. P. to 22.42 ka B. P.(sample section between 99.5 mm and 437.0 mm). Our new δ18O record suggests that the total duration of H2 termination spans for 844±3 years (error is determined by the annual fluorescent lamination counting). The termination of the event occurred from 24.280±0.028 ka B. P. to 23.436±0.028 ka B. P. inferred by a δ18O gradual shift of ca. 1.9 ‰. This process incorporates two negative excursions, from 24.28 ka B. P. to 24.17 ka B. P. and 23.90 ka B. P. to 23.44 ka B. P. and a relatively stable period from 24.17 ka B. P. to 23.90 ka B.
作者
董西瑀
程海
Kathayat Gayatri
张帆
李瀚瑛
张海伟
赵景耀
宁有丰
李向磊
成星
曲晓丽
Dong Xiyu;Cheng Hai;Kathayat Gayatri;Zhang Fan;Li Hanying;Zhang Haiwei;Zhao Jingyao;Ning Youfeng;Li Xianglei;Cheng Xing;Qu Xiaoli(Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710054, Shaanxi;Department of Earth Sciences, University of Minnesota, Minneapolis, MN 55455, USA;State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Shaanxi;University of Chinese Academy of Sciences, Beijing 100049;State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710054, Shaanxi)
出处
《第四纪研究》
CAS
CSCD
北大核心
2019年第4期878-893,共16页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:41888101和41731174)资助.
关键词
H2事件
亚洲季风
乞拉朋齐洞
年纹层石笋
H2 Event
Asian monsoon
Cherrapunji Cave
annual laminated stalagmite
