MIS 4时期亚洲夏季风变化的高分辨率石笋记录

发布时间：2018-05-05 18:20

本文选题：亚洲夏季风 + 石笋　；参考：《西南大学》2017年硕士论文

【摘要】：亚洲夏季风(Asian Summer Monsoon,ASM)是全球气候系统的重要组成部分,对于沟通南北半球气候变化之间的联系具有重要作用。近十几年来,科学家利用多种古气候记录载体针对ASM的演变进行了大量研究,然而,这其中高分辨率且具有精确定年的石笋记录主要集中于深海氧同位素阶段(Marine Oxygen Isotope Stages,MIS)1-3时期,MIS 4时期的石笋记录多存在分辨率较低或记录不完整等不足。MIS 4时期北半球夏季太阳辐射强度减弱,冰量上升、海平面下降,是末次冰期中与末次冰盛期相当的低温时期,研究这一时段,有助于全面理解末次冰期ASM的演化过程和驱动机制及其在全球气候系统中所起的作用。此外,最初发现于北大西洋沉积物岩芯记录的Heinrich(H)6事件的年代由于超过14C测年上限而一直存在争议,冰芯时标GICC05在早于60 ka BP时段的误差已超过2600年,急需得到校正。本文以采自重庆市南川区金佛山羊口洞的JFYK7石笋和奉节县新崖洞的XY2石笋为研究对象,利用高精度的U-Th测年技术和氧稳定同位素分析技术建立了MIS 4时期高分辨率的亚洲夏季风演变历史。通过与全球多种古气候记录进行对比探讨ASM的变化模式和可能的驱动机制,并且利用误差小于0.5%的230Th年龄对格陵兰间冰阶(GIS)和H事件的年代进行了精确标定,为冰芯时标的校正提供了参考。通过分析石笋JFYK7和XY2的δ~(18)O记录发现,在本文研究时段尽管在千年尺度上ASM变化与北纬30°夏季太阳辐射变化存在差异,但在轨道尺度上夏季太阳辐射仍是驱动ASM变化的直接动力。在千年尺度上,JFYK7和XY2石笋δ~(18)O记录了5个亚洲夏季风偏强时期,分别对应于格陵兰冰芯记录的GIS 17-21事件。此外还记录了3个δ~(18)O偏正的时期分别发生在59.4-61.5 ka BP,70.9-73.1 ka BP,73.9-75.4 ka BP,这些亚洲夏季风减弱事件也可以在NGRIP记录中发现其相对应的冷事件。这表明在千年尺度上,亚洲夏季风主要受北高纬地区气候变化的影响。通过与葫芦洞、山宝洞石笋记录,阿拉伯海记录对比发现,尽管存在一些由分辨率和测年误差导致的差异,总体上在本文研究时段东亚夏季风与印度夏季风在千年尺度上的变化是一致的,可能是由于二者共同响应于北高纬地区的气候变化。与南半球巴西石笋记录对比发现,南美夏季风与亚洲夏季风之间在千年尺度上呈反相对应,可能是热带辐合带(ITCZ)位置的南北移动和Hadley环流的不对称变化所致。利用误差小于0.5%的230Th年代,对GIS 17-21的年代进行了精确标定。与冰芯记录对比发现,石笋JFYK7记录的GIS 17的年代与NGRIP在GICC05时标下的记录在误差范围内非常一致,这也得到ASM地区其他石笋记录的支持。石笋记录的GIS 18的发生时间早于GICC05modelext冰芯时标,而在GIS 19-21的年代上石笋记录又晚于冰芯记录。这说明冰芯GICC05modelext时标在该时段的精度需要进一步提高,而石笋记录可以为其提供参考。石笋JFYK7和XY2清晰记录了H6事件,这是在AS M地区的石笋记录中首次完整地发现H6事件,本文精确地将其起止时间分别标定为61.5±0.2 ka BP和59.4±0.2 ka BP。通过对亚洲季风区各地的古气候记录资料分析表明,H6时期亚洲夏季风强度显著减弱,南亚、中国北方和南方均为降水减少的干旱环境。GIS 18向H6的转换过程在格陵兰冰芯记录和北半球中低纬度地区的古气候记录中存在显著差异,中国石笋记录以及阿拉伯海岩芯记录均表现为GIS 18向H6转变的过程中亚洲夏季风经历了长达4 ka的缓慢减弱过程,而格陵兰温度却在0.25 ka内迅速降低。通过对比南极冰芯记录我们推测,这种异常现象可能是南半球温度逐渐上升导致的热带辐合带(ITCZ)位置南移以及跨赤道气流减弱造成的。
[Abstract]:The Asian Summer Monsoon (ASM) is an important part of the global climate system. It plays an important role in communication between the climate changes in the northern and southern hemispheres. In the past decade, scientists have used a variety of paleoclimate records to study the evolution of ASM. However, the high resolution and precise determination of ASM has been made. The record of Stalagmite in the year is mainly concentrated in the period of the Marine Oxygen Isotope Stages (MIS) 1-3. The record of Stalagmite in the period of MIS 4 has many low resolution or incomplete records. The summer solar radiation intensity in the northern hemisphere of the northern hemisphere is weakened, the amount of ice rises, and the sea level falls, which is the phase of the last glacial and the last glacial period. During the low temperature period, the study of this period will help to understand the evolution and driving mechanism of ASM in the last glacial period and its role in the global climate system. In addition, the Heinrich (H) 6 event, which was first discovered in the North Atlantic sediment core, has been disputed over the upper limit of the 14C dating, and the ice core GIC The error of C05 in the period of 60 Ka BP is more than 2600, and it is urgent to be corrected. In this paper, the JFYK7 stalagmite from Jinfu goats cave in Chongqing Nanchuan district and the XY2 stalagmite of the new cliff cave in Fengjie county were studied. The high resolution Asian summer summer of the period of the MIS 4 period was established by high precision U-Th dating technique and oxygen stable isotope analysis technique. The history of wind evolution. By comparing the variation patterns and possible driving mechanisms of ASM with a variety of paleoclimate records in the world, and using the 230Th age of less than 0.5% of the error, the age of the ice order (GIS) and H events of Greenland is calibrated accurately, which provides a reference for the calibration of the ice core time mark. By analyzing the delta ~ (1) of the JFYK7 and XY2 of the stalagmite. 8) O records found that in the study period, although there is a difference between the ASM changes on the Millennium scale and the summer solar radiation in the north latitude 30 degrees, the solar radiation in the orbital scale is still the direct driving force to drive the change of ASM. On the Millennium scale, the JFYK7 and XY2 stalagmite delta ~ (18) recorded 5 Asian summer monsoon strong periods, corresponding to the lattice, respectively. The GIS 17-21 event recorded by the Ling LAN ice core. In addition, 3 delta ~ (18) O deviation periods are recorded in 59.4-61.5 Ka BP, 70.9-73.1 Ka BP, 73.9-75.4 Ka BP. These Asian summer monsoon weakening events can also be found in the NGRIP records of their corresponding cold events. This indicates that the Asian summer monsoon is mainly North High Latitude on the Millennium scale. The effect of climate change in the region. Through the record of the Stalagmite in Hulu cave and the mountain treasure cave, the Arabia sea record contrasts that, although there are some differences caused by the resolution and the dating error, the East Asian summer monsoon and the India summer monsoon are in accordance with the variation in the Millennium scale in this study period, which may be due to the common response of the two. The climate change in the northern high latitude region. Compared with the Brazil stalagmite records in the southern hemisphere, the South American Summer Monsoon and the Asian summer monsoon are opposite to the Millennium scale, which may be caused by the North-South movement of the tropical convergence zone (ITCZ) and the asymmetrical change in the Hadley circulation. Using the 230Th age of less than 0.5% error, the age of GIS 17-21 Accurate calibration. Compared with ice core records, it was found that the age of GIS 17 recorded by stalagmite JFYK7 was very consistent with the record of NGRIP at GICC05, which was also supported by other stalagmite records in ASM area. The time of GIS 18 recorded in the stalagmite was earlier than that of GICC05modelext ice core, but in the age of GIS 19-21, the stalagmite was in the age of GIS 19-21. The record is later than the ice core record. This indicates that the precision of the ice core GICC05modelext at this time period needs to be further improved, and the stalagmite record can provide reference for it. The stalagmite JFYK7 and XY2 clearly record the H6 events. This is the first complete discovery of H6 events in the stalagmite records in the AS M region. This article accurately demarcate its starting time. The analysis of paleoclimate records of 61.5 + 0.2 Ka BP and 59.4 + 0.2 Ka BP. showed that the Asian summer monsoon intensity decreased significantly during the H6 period, South Asia, North and South China were all precipitation decreasing arid environment.GIS 18 to H6 in Greenland ice core record and middle and low latitudes of northern hemisphere palaeoatmosphere. There are significant differences in the waiting record. China's stalagmite records and Arabia Hai Yan core record that the Asian summer monsoon experienced a slow decline of 4 Ka during the transition from GIS 18 to H6, while the Greenland temperature decreased rapidly within 0.25 Ka. By comparing Antarctic ice cores, we speculate that this anomaly may be South half The gradual increase in the temperature of the sphere results in the southward movement of the tropical convergence zone (ITCZ) and the weakening of the cross equatorial flow.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P532

【参考文献】