| Summary: | 发生在12.9~11.6 kA bP的一次北半球气候快速变冷——新仙女木(yd)事件在过去30年来一直是古气候研究的热点。当下由于人类活动引起全球变暖,研究类似的快速气候变化事件及其触发机制对于预测未来气候变化具有重要意义。然而时至今日,科学界对yd事件的发生时间、气候效应、触发机制及其全球性意义依然存在很大争议。对比多个高分辨率记录探讨了yd事件的发生时间及其年代学意义,详细总结了南、北半球中高纬地区及低纬地区近年来新发现的yd事件的记录及其气候效应,重点讨论了yd事件触发机制假说的发展与争议,并结合yd事件的研究现状提出了未来研究热点和重要方向。 The Younger Dryas(YD) event which lasted from 12.9 ~ 11.6 ka BP is a rapid return to near-glacial conditions with a major impact on global climate that punctuated last glacial-Holocene transition period.The YD event was firstly found in records of mid-high latitude Northern Europe and North Atlantic vicinities and later identified broadly in North Pacific Oceans,Asia,North America,tropics and even in South Hemisphere.The mechanism of YD event is not clear although tremendous efforts have been paid over the past 30 years.Even the precise timing,duration and global impact remain ambiguous.The understanding of the magnitude of YD-like event in temporal and spatial scales andits forcing mechanism may help us to forecast the possible environmental and ecological impacts in global scale due to anthropogenic forcing.This article reviewed the progress of studies on the YD event,including the most recent dating of the onset and geographic pattern of climatic impacts,and particularly the triggering mechanisms proposed in recent years.The disparities of precise dates among records for the YD onset may result from counting mistakes,regional environmental responses and rapid fluctuation of atmospheric14 C.Globally,the YD event was characterized by abrupt climate change with increasing anomalies in magnitude toward the poles and opposite signs between Hemispheres,which modulated by bipolar seesaw mechanism.It is generally accepted that the YD event is caused by a slowdown Atlantic Meridional Overturning Circulation(AMOC).However,the triggering mechanism of this slowdown is debatable.Besides the earliest hypothesis of Lake Agassiz outburst,alternative mechanisms such as meltwater discharge into Arctic Ocean,extraterrestrial impact or atmospheric circulation forcing have been proposed under various supportive evidences.Tropical processwas suggested to play an additional role in abrupt climate change,of which high latitude was thought to be the modulator.The newest hypothesis suggested that YD event was an integral part of natural climate oscillation rather than a freak excursion.Finally,future directionstohave a complete understanding of the mechanisms of YD event are provided. 国家自然科学基金项目重大研究计划“南海水体硝酸盐动力学与水团示踪”(编号:91328207);国家自然科学基金面上项目“中国边缘海沉积物氮同位素时空变化与控制因子”(编号:41176059)资助
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