东亚季风气候对Heinrich2事件的响应:来自石笋的高分辨率记录

据湖北省神农架天鹅洞一支石笋11个230Th年龄和254个δ18O数据,建立了28.5～22.0kaB.P.同位素分辨率平均约30a的东亚季风气候变化序列。该石笋δ18O曲线与南京葫芦洞石笋记录在重叠时段基本一致,说明本区石笋δ18O反映了区域性东亚季风经向环流特征。在24.3kaB.P.左右,石笋δ18O明显正偏,持续时间近1ka,指示一次显著的弱夏季风事件,与北大西洋倒数第二次冰漂碎屑事件(Heinrich2)同步发生,可视为东亚季风气候对H2事件的响应。高分辨率的δ18O序列揭示了H2事件的内部结构特征:(1)事件发生的突变性,石笋δ18O记录指示事件发生时在100a内δ18O从-8.59‰迅速正偏为-6.75‰,振幅达1.84‰;(2)事件结束的渐变性,δ18O正偏到-6.75‰后便以阶梯状缓慢负偏到-8.86‰至事件结束,持续时间近900a。这一过程与末次盛冰期东亚季风气候H1事件表现的季风强弱转换方式基本一致,说明末次盛冰期东亚季风气候H型事件具有共同的内部结构特征。研究表明,末次盛冰期东亚季风气候H事件的突变可能受北大西洋驱动并经青藏高原冰川变化放大。     

MIS 3晚期东亚季风强度和DO事件年龄

基于神农架山宝洞石笋(SB46)的9个230Th年龄和326个氧同位素数据,建立了末次冰期32.2～26.7kaB.P.和17.0～15.4kaB.P.的东亚季风降水序列。该序列和同一洞穴全新世石笋记录的对比发现,在MIS3晚期东亚季风区可能存在极强夏季风降水事件,相当于全新世季风强度,可能与岁差旋回太阳辐射及海陆水汽潜热释放增强有关。与葫芦洞石笋δ18O记录和格陵兰冰芯δ18O记录对比表明,东亚夏季风千年尺度气候振荡与高北纬地区海-气快速重组存在遥相关效应。山宝洞石笋年龄与葫芦洞石笋和格陵兰冰芯时标(SS09sea)在定年误差范围内基本一致,但山宝洞石笋与冰芯记录在DO事件的年龄、波形和持续时间上更为一致,不仅进一步说明了低纬季风气候与极地气温同步变化,而且有效地弥补了葫芦洞记录在这一时段的不足。     

179～129 ka B.P.时段千年尺度气候事件的湖北神农架石笋记录

根据湖北神农架1支石笋(SB11)13个230Th年龄和638个δ18O数据,重建了179～129 ka B.P.时段连续的高分辨率东亚夏季风历史.轨道尺度上石笋δ18O曲线呈现2个岁差旋回,指示东亚夏季风强弱变化受北半球夏季日辐射能量变化驱动.一系列千年尺度季风事件叠加于轨道尺度季风气候旋回上,与已有的东亚季风事件、北大西洋冰漂碎屑事件及地中海降温事件具有比较相似的变化规律,进一步证明了倒数第二次冰期千年尺度气候事件在北半球具有普遍性.山宝洞石笋记录与葫芦洞石笋记录的对比结果表明,最后两个冰期旋回千年尺度事件发生频率及变化幅度非常相似,有力地支持了千年尺度气候事件的冰量驱动模式.     

东亚季风MIS 3早期DO事件的亚旋回及全球意义

根据湖北永兴洞石笋(YX51)10个U/Th年龄,470组氧、碳同位素数据建立了深海氧同位素3阶段(MIS3)早期57.7~35.6kaB.P.期间东亚夏季风演化时间序列。在发育时段,千年尺度δ18O峰谷变化与高纬冰芯记录的Dansgaard-Oeschger(DO)事件一致;δ13C呈现出与δ18O正相关同步演化特征,但受区域环境影响,在事件内部细节上存在差异。区域对比表明,同一季风区的永兴洞和葫芦洞石笋δ18O指示的季风降水同位素组成具有本质上一致性;高低纬记录对比显示,千年尺度的峰谷变化一一对应,反映热带辐合带(ITCZ)水汽传输能力、平均位置变化对东亚季风和高北纬气候具有重要影响。在DO13至DO15事件内部,永兴洞石笋δ18O记录了显著的双峰特征,说明低纬季风强度变化和格陵兰冰芯δ18O揭示的次级暖峰具有一致对应关系,指示大气快速传输机制在高低纬环境突变中起着重要作用。     

中国黄土高原西缘甘肃万象洞MIS 5石笋δ18O记录与南方地区石笋记录的对比研究

位于青藏高原与黄土高原过渡带的甘肃武都万象洞石笋WXSM51和WXSM52提供了MIS 5(118～79 kaB.P.)高分辨率的δ18O记录.研究表明,万象洞石笋δ18O值与夏季风强度呈负相关关系,与我国西南部的贵州董歌洞石笋δ18O记录有良好的对应关系,并与高纬度的格陵兰NGRIP冰芯δ18O记录和65°N太阳辐射强度有很好的一致性,说明万象洞石笋δ18O记录了118～79 kaB.P.期间亚洲季风强度的变化,同时也说明东亚季风强度的变化和全球气候变化同步,而且主要受控于北半球太阳辐射强度的变化.同时它与地中海碳酸盐记录有很好的相似性,和巴西石笋δ18O记录在千年尺度上表现出相反的变化趋势,说明东亚季风区、地中海地区以及巴西季风区之间存在密切的联系,指示了南北半球气候在千年尺度上存在"跷跷板"(seesaw)现象.万象洞石笋δ18O记录的MIS 5b与MIS 5a突发性转换,与NGRIP冰芯δ18O记录相似,而与神农架记录存在差异,说明万象洞地区对亚洲季风强度的响应更为敏感.     

黄土高原西部石笋记录的H2事件特征

青藏高原与黄土高原过渡带的甘肃武都万象洞位于现代夏季风的边缘区, 对气候变化极为敏感.通过洞内一支石笋WX40D的6个高精度TIMS-U系定年数据和616个样品的氧同位素测定, 建立了28.3~23.0 ka B.P., 分辨率约为10年的亚洲季风气候变化序列. 石笋δ18O记录揭示Marine Isotope Stage 2 (MIS2)早期东亚季风气候具有10~100 a尺度高频震荡特征, 从中识别出北大西洋Heinrich 2 (H2)特强冷事件, 且记录显示该事件开始于24.6 ka B.P., 呈突发式降温之后持续跌宕式降温变化. 对比研究发现, 万象洞石笋δ18O记录H2事件与葫芦洞、天鹅洞的石笋记录有差别, 但是与湖南金滩湾洞穴石笋δ18O记录、33°N太阳辐射强度以及极地GRIP冰心记录变化趋势一致, 表明季风边缘区气候变化主要受北半球中纬度太阳辐射能背景、北大西洋冰漂碎屑带的扩张以及低纬太平洋海表温度变化等因素的控制, 同时万象洞特殊的地理位置使得区域气候更易受到与极地气候有密切联系的亚洲冬季风和西风环流变化的影响.      

山东半岛石笋记录的倒数第二次冰消期δ18O变化特征及其气候环境意义

文章基于山东半岛岩溶洞穴(上小峰洞)一根长约41 cm的石笋SD1的铀系测年和稳定同位素组成分析,获得138. 0~125. 8 ka B. P.平均分辨率为30年的石笋δ18O 和δ13C时间序列,并据此讨论了倒数第二次冰消期区域气候和环境变化的特征及与全球变化的联系.在倒数第二次冰消期,上小峰洞石笋( SD1)δ18O的变化与中国南方石笋δ18O的变化具有类似的阶段变化特征,进一步确认了冰消期北大西洋气候对亚洲季风的重要影响.通过对山东石笋高分辨δ18O记录进行时间序列分析,发现该记录存在显著的约60年、 75年和1620年周期,表明太阳活动和北大西洋涛动与该地区气候变化有紧密的联系.同时,通过对比东亚季风区高分辨率石笋记录,认为在倒数第二次冰消期为"两步冰消"的变化特征.除此之外,上小峰洞石笋碳酸盐δ18O冰期和间冰期平均值的差异仅为0. 7‰,远小于内陆洞穴石笋碳酸盐δ18O冰期和间冰期平均值的差异(羊口洞约为1. 4‰,董哥洞约为2. 2‰,三宝洞约为2. 4‰).这一显著差异可能主要源于海岸线迁移造成的海陆格局的变化对区域季风降水及降水氧同位素组成的重要影响;并且冰期-间冰期海平面变化对近海环境记录、大陆架下垫面、海洋沉积物气候指标等都可能产生影响.     

末次冰期贵州七星洞石笋高分辨率气候记录与Heinrich事件

通过对贵州都匀七星洞Q4、Q6石笋进行高精度的TIMS-U系测年和氧同位素分析,建立了末次冰期60．5kaB P以来都匀凯酉地区高分辨率的古气候变化时间序列。通过与格陵兰GISP2冰心的δ^18O曲线对比分析,初步揭示并探讨了末次冰期以来反映的短时间尺度气候快速变化的D-O旋回事件1-18和Heinrich事件H1～H5在黔南七星洞中的石笋记录,并对冷事件发生的年代给出了界定。研究表明,黔南60．5kaB P以来石笋记录冷暖事件所反映出的古季风环流变化,明显受北大西洋气候振荡的影响,显示与北极地区存在着古     

晚更新世东亚季风气候不稳定性的洞穴石笋同位素证据

据南京汤山葫芦洞石笋的23个热电离质谱测年结果和分辨率达100-200a的氧、碳稳定同位素测试数据，讨论了75-35kaBP期间东亚季风气候的高频振荡特征。石笋氧同位素值的波动范围介于-9.165‰～5.456‰之间，相邻峰谷的变幅可达2‰～3‰，由其构成的16个气候不稳定性事件与格陵兰冰心δ^18o记录中IS8-IS20和北大西洋冰漂碎屑事件H4-H6有良好的对比关系，揭示了东亚季风气候变化与高纬极地大气温度变化存在着动力机制上的联系。石笋碳同位素记录呈现类似于δ^18O记录的高频振荡形式，反映了洞穴了覆植被类型对存在着动力机制上的联系。石笋碳同位素记录呈现类似于δ^18O记录的高频振荡形式，反映了洞穴上覆植被类型对气候变化的快速响应。石笋稳定同位素曲线上72ka BP左右的快速降温事件与印度尼西亚Toba火山喷发事件基本一致。有可能说明是更新世全球气候事件的发生并非单一源于北大西洋深层水体的变化。     

东亚夏季风石笋记录中缺失格陵兰间冰段25?

东亚季风是全球气候系统的重要组成部分[1~6]。了解北大西洋地区温度变化和东亚夏季风之间的关系对了解东亚季风的控制机制具有重要意义。葫芦洞和董哥洞石笋δ18O记录显示距今75~10ka北大西洋地区千年尺度温度变化对东亚夏季风变化具有重要影响:较强的东亚夏季风与北大西洋地区较高气温对应,反之亦然[7,8]。但是,在此之前东亚夏季风变化与北大西洋地区温度变化之间是否具有类似的联系?到目前为止对这一问题尚没有明确的探讨。根据最近分别在意大利北部[9]和中国中部获得的石笋δ18O记录,笔者发现,北大西洋地区冰芯记录的间冰段(Greenland…     

Distinct climate change synchronous with Heinrich event one, recorded by stable oxygen and carbon isotopic compositions in stalagmites from China

Uranium-series dating of oxygen and carbon isotope records for stalagmite SJ3 collected in Songjia Cave, central China, shows significant variation in past climate and environment during the period 20-10 ka. Stalagmite SJ3 is located more than 1000 km inland of the coastal Hulu Cave in East China and more than 700 km north of the Dongge Cave in Southwest China and, despite minor differences, displays a clear first-order similarity with the Hulu and Dongge records. The coldest climatic phase since the Last Glacial Maximum, which is associated with the Heinrich Event 1 in the North Atlantic region, was clearly recorded in SJ3 between 17.6 and 14.5 ka, in good agreement in timing, duration and extent with the records from Hulu and Dongge caves and the Greenland ice core. The results indicate that there have been synchronous and significant climatic changes across monsoonal China and strong teleconnections between the North Atlantic and East Asia regions during the period 20-10 ka. This is much different from the Holocene Optimum which shows a time shift of more than several thousands years from southeast coastal to inland China. It is likely that temperature change at northern high latitudes during glacial periods exerts stronger influence on the Asian summer monsoon relative to insolation and appears to be capable of perturbing large-scale atmospheric/oceanic circulation patterns in the Northern Hemisphere and thus monsoonal rainfall and paleovegetation in East Asia. Climatic signals in the North Atlantic region propagate rapidly to East Asia during glacial periods by influencing the winter land-sea temperature contrast in the East Asian monsoon region.     

神农架天鹅洞石笋76～58 kaB.P.时段DO事件

据神农架高海拔天鹅洞一支石笋9个230Th年龄和332组氧、碳同位素数据,建立了76～58 kaB.P. Dansgaard Oeschger (DO)事件时间序列,揭示了深海氧同位素4阶段(MIS4)东亚季风降水百年尺度变化过程。天鹅洞和葫芦洞石笋、格陵兰NGRIP冰芯δ18O对比显示,天鹅洞记录DO18事件暖湿程度相当于深海氧同位素3阶段(MIS3)水平,其振幅类似于格陵兰冰芯δ18O记录。起始时间上,天鹅洞记录DO18事件在710年230Th测年误差范围内和葫芦洞记录保持一致,并支持了NGRIP冰芯记录对应时标。在全球降温背景下,如此典型DO事件指示了强季风降水过程。70 kaB.P.左右,冰芯DO19事件至少老于石笋记录约950年,远大于700年左右的230Th测年误差,对老于该时段的冰芯时标需高分辨率地质记录进一步验证。69.09～64.64 kaB.P.（ DO19ˊ~18）期间,冰芯记录的百年尺度峰谷变化和天鹅洞石笋记录一一对应,反映了低纬热带海洋和北大西洋温盐环流之间耦合作用。     

The East Asian monsoon during MIS 2 expressed in a speleothem δO record from Jintanwan Cave, Hunan, China

Stalagmite J1 from Jintanwan Cave, Hunan, China, provides a precisely dated, decadally resolved δ¹⁸O proxy record of paleoclimatic changes associated with the East Asian monsoon from ∼29.5 to 14.7 ka and from ∼12.9 to 11.0 ka. At the time of the last glacial maximum (LGM), the East Asian summer monsoon weakened and then strengthened in response to changes in Northern Hemisphere insolation. As the ice sheets retreated the East Asian summer monsoon weakened, especially during Heinrich event H1, when atmospheric and oceanic teleconnections transferred the climatic changes around the North Atlantic to the monsoonal regions of Eastern Asia. A depositional hiatus between ∼14.7 and 12.9 ka leaves the deglacial record incomplete, but an abrupt shift in δ¹⁸O values at ∼11.5 ka marks the end of the Younger Dryas and the transition into the Holocene. Comparisons of the J1 record to other Chinese speleothem records indicate synchronous climatic changes throughout monsoonal China. Further comparisons to a speleothem record from western Asia (Socotra Island) and to Greenland ice cores support hemispherical-scale paleoclimatic change. Spectral and wavelet analyses reveal centennial- and decadal-scale periodicities that correspond to solar frequencies and to oscillations in atmospheric and oceanic circulation.     

Decoupling of the East Asian summer monsoon and Indian summer monsoon between 20 and 17 ka

Marine Oxygen Isotope Stage (MIS) 2, with its profound environmental and climatic changes from before the last glacial maximum (LGM) to the last deglaciation, is an ideal period for understanding the evolution of the East Asian summer monsoon (EASM) and Indian summer monsoon (ISM), two Asian monsoon sub-systems. With 875 stable oxygen isotope ratios and 43 ²³⁰Th dates from stalagmites in Sanxing Cave, southwestern China, we construct and interpret a new, replicated, Asian summer monsoon (ASM) record covering 30.9–9.7 ka with decadal resolution. δ¹⁸O records from this site and other reported Chinese caves display similar long-term orbitally dominated trends and synchronous millennial-scale strong and weak monsoonal events associated with climate changes in high northern latitudes. Interestingly, Sanxing δ¹⁸O and Arabian Sea records show a weakening ISM from 22 to 17 ka, while the Hulu and Qingtian records from East and Central China express a 3-ka intensifying EASM from 20 to 17 ka. This decoupling between EASM and ISM may be due to different sensitivities of the two ASM sub-systems in response to internal feedback mechanisms associated with the complex geographical or land-ocean configurations.     

长江中游石笋年层厚度作为东亚夏季风强度代用指标的研究

利用Olympus偏光显微镜,直接在光学薄片上对长江中游和尚洞HS4石笋进行微层计数,并测量微层厚度。微层计数结果与其对应的UTh定年结果相吻合,证明该支石笋微层为年层;统计分析说明,该石笋的年层厚度变化响应近百年来东亚夏季风强度变化,两者呈负相关,说明长江中游石笋生长受东亚夏季风制约。因而,长江中游石笋年层厚度可以作为高分辨率的东亚夏季风强度代用指标。     

贵州石笋记录的中晚全新世东亚夏季风变化

研究全新世典型气候突变事件的内部结构及区域特征,有助于明晰季风气候突变事件的成因机制。通过对贵州七星洞石笋14个高精度²³⁰Th定年和779个氧同位素数据的分析,重建了过去6 380～2 700 yr B.P.时段平均分辨率达4.7年的东亚夏季风演化序列。该石笋δ¹⁸O值整体上呈逐渐偏正的特征,指示中晚全新世以来东亚夏季风持续变弱的趋势。叠加在此长期季风减弱变化趋势上,最为显著的百年尺度振荡主要发生在4 548～3 715 yr B.P.时段,对应于4.2 kyr B.P.事件。该记录与同区域董哥洞石笋δ¹⁸O记录一致,均显示在此事件内部并非持续干旱,而是具有两次显著的季风强降雨期。相似的季风强降雨期在我国北方气候记录中也有体现。在更大的空间尺度上,这种4.2 kyr B.P.事件的内部结构特征与澳洲—印度尼西亚(澳—印)季风区的石笋记录结构相对应,但呈显著的反相位耦合关系,证实了亚洲与澳—印季风间的动力学联系。此外,该事件结构与ENSO记录的耦合暗示了4.2 kyr B.P.事件的发生可能与热带太平洋密切相关。     

Speleothem‐derived Asian summer monsoon variations in Central China, 54–46 ka

The oxygen isotope signature (δ¹⁸O) of stalagmite SI3 collected from Shizi Cave in north‐east Sichuan Province provides an Asian Summer Monsoon (ASM) record in Central China for the period 54–46 ka. The SI3 δ¹⁸O record clearly shows a negative δ¹⁸O excursion centred around 49.4 ka, which was reported in Hulu Cave in East China but not identified in the speleothem records from South‐west China. As a whole, this record displays a higher coherence with the two Hulu records from East China than with the speleothem δ¹⁸O records from South‐west China, suggesting that at 54–46 ka, Central China was influenced more by the East Asian Summer Monsoon than by the Indian Summer Monsoon. It also displays a significant negative δ¹⁸O excursion at 47.5–46.6 ka, which is not clearly documented in two other speleothem δ¹⁸O records previously reported from South‐west China. This suggests that details of the Greenland interstadial 12 warrant further investigations in future in monsoonal China. The SI3 δ¹⁸O record displays more significant centennial‐scale variations than the other four speleothem δ¹⁸O records from East and South‐west China, which may be due to the fact that the study site is closer to the north‐west boundary of the ASM and more sensitive to variations of the ASM than East and South‐west China. Copyright © 2011 John Wiley & Sons, Ltd.     

Spatial variations of monsoonal rain in eastern China: Instrumental, historic and speleothem records

We select four caves and their nearby cities in the monsoonal region of China for studying the relationships among precipitation, temperature, summer monsoon intensity and stalagmite δ¹⁸O. The instrumental, historic and stalagmite δ¹⁸O records from these areas show strong spatial disparities on annual to decadal scales, so that climatic conditions in a single location cannot represent these of the entire eastern China. On time scales <500 years, stronger summer monsoon may lead to higher rainfall in some locations but not over eastern China. Correlation between the summer monsoon strength and precipitation is not only location-dependent but also changes with time. One may not use the paleoclimatic pattern of cold–dry and warm–wet on glacial/interglacial ages throughout all time scales for climatic conditions in the monsoonal region. On centennial to millennial scales, stalagmite δ¹⁸O variation trend from eastern China resemble solar irradiance with lighter δ¹⁸O corresponding to increased solar irradiance, and vice versa. The similar trends may reflect climatic feedbacks link to solar forcing to cause changes in the summer monsoon intensity and/or in monsoonal circulation. Changes in monsoonal circulation and intensity affect (1) summer rainfall intensity, (2) summer/winter precipitation ratio, or (3) ratio of moisture from Indian/Pacific oceans, or a combination of the three. Thus, a speleothem δ¹⁸O record may not be proper to be used as a proxy of paleo-precipitation amount, especially on short time scales. Based on the four stalagmite δ¹⁸O records during the last 2000 years, EASM strength decreased from AD 200 to AD 500, and from AD 1300 to AD 1600 (the 1st half of the Little Ice Age), whereas EASM strength increased from AD 1600 to AD 1900 (the 2nd half of the Little Ice Age). The EASM strength has weakened since early 1900’s.     

小冰期东亚夏季风快速变化特征:湖北石笋记录

研究小冰期的结构特征及动力机理有助于理解全球增暖和极端气候事件的原因。基于湖北永兴洞总长为120 mm的YX275石笋7个高精度230Th年龄和120个氧同位素数据,重建了1361~1955 A.D.时段分辨率达5 a的东亚夏季风降水变化序列。该石笋δ^18O值在-7.8 ‰^-9.3 ‰范围内波动,长期趋势呈现出先缓慢增大后减小的变化特征,整体呈下凹形态。该记录与中国季风区北部和南部石笋记录变化大体一致,指示小冰期发生时东亚夏季风水循环发生减弱变化。在百年-数十年尺度上,YX275石笋记录的小冰期内5次显著季风降水减弱事件与南部贵州董哥洞、织金洞石笋记录变化一致,但不同于北方大鱼洞、九仙洞、黄爷洞和万象洞石笋记录的5次小幅度季风旋回特征,表明小冰期时中国南北部夏季风降水在短时间尺度上可能存在着区域差异。该记录与太阳总辐照度记录和北半球温度记录变化一致,表明太阳总辐照度和北半球温度变化对东亚夏季风水文变化有重要驱动作用。