Knowledge Resource Center for Ecological Environment in Arid Area
| 青藏高原地区近千年气候变化时空特征的初步研究 | |
| 其他题名 | Preliminary study on spatiotemporal pattern of climate change during past millennium over Tibet Plateau |
| 张彦成 | |
| 出版年 | 2012 |
| 学位类型 | 硕士 |
| 导师 | 侯书贵 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 青藏高原在全球气候系统中具有重要作用，研究青藏高原地区近千年气候变化有助于理解区域及全球尺度的气候演化过程；同时，由于大面积冰冻圈（冰川-积雪-冻土）的存在，研究青藏高原地区近千年的气候变化对预测未来气候情景下其冰冻圈变化及其对我国西北干旱区水资源与生态环境安全的影响具有重要科学意义。青藏高原地区主要受西风带气候与亚洲季风气候的共同影响，基于反映历史时期气候与环境变化的各种代用资料（如，树轮、石笋、冰芯、湖泊沉积、文献记载等），国内外诸多学者已就青藏高原地区近千年气候变化的基本格局及区域特征等方面展开了大量工作。然总体而言，由于青藏高原地区记录近千年气候变迁的高分辨率代用资料较为稀缺且分布极不均匀，这也就限制了对青藏高原地区近千年气候变化特征的全面认识。鉴于此，本论文主要通过收集近年来获得的反映青藏高原地区近千年气候变化的高分辨率代用资料（主要为树轮、石笋、冰芯），利用综合对比分析和经验正交函数（EOF）等数学统计方法，以期能够在青藏高原地区近千年气候变化的基本格局与区域特征问题上的认识有所深化。 \n本论文中，共收集到反映青藏高原地区近千年温度变化的高分辨率代用资料15条。基于上述15条资料的11滑动平均序列：首先，本文尝试以综合比例法（composite-plus-scaling, CPS）综合重建了青藏高原地区近千年气候变化的基本格局；其次，通过对上述15条序列进行经验正交函数（EOF）分析，以期对青藏高原地区近千年气候变化典型特征（中世纪暖期‘MWP’、小冰期‘LIA’及20世纪暖期等）的区域差异有进一步的认识。以特征值＞1及因子载荷＞0.6来判断，上述15条序列的EOF分析结果可提取六个主分量：第一主分量（PC1）主要包括青海乌兰及都兰3条树轮年表序列，可能反映了高原东北部的气候变化特征；第二主分量（PC2）主要包括天山南部（吉尔吉斯斯坦境内）与喀喇昆仑山西北部（巴基斯坦境内）3条树轮年表序列，可能反映了喀喇昆仑地区的气候变化特征；第三主分量（PC3）主要包括达索普冰芯δ18O记录及东绒布冰芯δD记录2条同位素序列，可能反映了高原南部的气候变化特征（如，季风环流强度信号等）；第四主分量（PC4）主要包括古里雅冰芯δ18O记录1条序列，可能反映了高原西部的气候变化特征；第五主分量（PC5）主要包括普若岗日冰芯δ18O记录1条序列，可能反映了高原中北部地区的气候变化特征；第六主分量（PC6）主要包括西藏昌都树轮年表1条序列，可能反映了高原中东部地区的气候变化特征。 \n综合重建序列表明，青藏高原地区中世纪暖期（MWP）约持续到1300s前后，小冰期（LIA）约发生于1450s-1870s，此后温度在波动中逐渐升高。这一基本格局与以数十年分辨率代用资料重建的青藏高原近两千年温度变化序列基本一致；同时，也与世纪尺度上的太阳活动变化（de Vries “德弗里斯周期”，约200年）相吻合。对比还发现，本论文重建的序列中MWP温暖程度与北半球及我国中东部地区的重建结果基本相似，也与20世纪前半页的幅度可比；重建序列还显示青藏高原地区LIA相对寒冷的气候特征并没有我国中东部地区那么显著（如，17及19世纪）；另外，对20世纪以来的全球气候变暖，重建序列不仅反映了温度的升高趋势，也记录了1970s北半球的突然降温事件。 \nEOF分析结果揭示了青藏高原东北部、喀喇昆仑地区、高原南部、高原西部、高原中北部及高原中东部等6个子区域在过去近千年气候变化过程中典型特征（MWP、LIA及20世纪暖期）上的异同性：MWP在高原东北部、北部及喀喇昆仑地区约持续到12世纪初，而在高原南部约至1450s；LIA的寒冷气候特征在青藏高原的起止年代较为统一，约为1450s-1870s；LIA期间的冷波动在高原东北部及西部地区约为1450s-1520s、1650s-1750s、1780-1850s等3个时期，在喀喇昆仑地区约为1450s-1650s、1740s-1780s、1820s-1850s等3个阶段（其中约1650s-1740s为温暖气候，且这一特征在高原北部冰芯δ18O序列中也有相关记录，但该时段对应于Maunder太阳活动极小期），而高原南部现有代用资料中并未明显记录上述冷波动事件；在近百年来全球升温的背景下，高原南部一些树轮年表则显示近百年的夏季温度存在一定下降趋势，通过高分辨率代用资料研究历史时期不同季节（冬、夏季）温度变化的一致性将有助于全面理解全球气候变暖的史实。 \n最后，需要指出的是，当前在青藏高原近千年气候变化综合集成研究中亟待解决的科学问题主要包括：1）更多气候指示明确的高分辨率气候变化单点重建序列，2）新的古气候综合集成研究方法等。同时，研究气候相对较暖的条件下热带大洋地区的区域水文循环变化（如，MWP期间的“印-太”暖池）对亚洲季风系统的影响或许有助于提高对当前全球气候变化集成研究的认识。 |
| 英文摘要 | Due to the critical role of Tibet Plateau (TP) in climate system, researching climate change during past millennium over TP would contribute greatly to understand global climate change. Moreover, with the cryosphere (glaciers, snow and permafrost) over TP, this work would also help to assess water resource and ecological security influenced by the ablation of cryosphere over TP under future climate scenario. Using abundant of archives implied past climate change (i.e., tree ring, stalagmite, ice core, lake sidement), scientists had made a great progress in this issue. However, generally, the exact course of climate change during past millennium over TP is still unclear due to the scarcity of paleoclimate records with high resolution in such region. By collecting the high resolution paleoclimate series reflecting climate change during past millennium over TP, this work aims to further study the spatiotemporal pattern of climate change during past millennium over TP through comprehensive and EOF analysis. \nTotally, we collect 15 high resolution paleoclimate records implying the climate change during past millennium over TP. By the decadal series of these 15 records collected in this study, we first reconstruct the general pattern of climate change during past millennium over TP by composite-plus-scaling method, and then the regional difference of climate anomalies during past millennium (e.g., Medieval Warm Period ‘MWP’; Little Ice Age ‘LIA’ and post-industrial warming) were further investigated by Empirical Orthogonal Function (EOF) method. According to the criteria consisting of eigenvalue >1 and factor loading >0.6, the first six PC would be extracted. The first PC, including three tree-ring chronologies from Wulan and Dulan, Qinghai, probably implys the past climate change in Northeast TP; The second PC, including three tree-ring chronologies from Southern Tien Shan (Kirghizia) and Northwest Karakorum (Pakistan), probably reflects past climate change in Karakorum area; The third PC, including the δ18O series from East Rongbuk and Dasuopu ice core, probably contains the common signal of past climate change in Southern TP (e.g., Asia monsoon circulation); The fourth PC, including the δ18O series from Guliya ice core, probably implys past climate change in Western TP; The fifth PC, including the δ18O series from Puruogangri ice core, probably implys past climate change in Northern TP; The sixth PC, including the tree-ring chronology from Changdu, probably implys past climate change in Eastern TP. \nComprehensive analysis of the 15 decadal series shows that MWP would last until ~1300s over TP, LIA would be occurred during 1450s-1870s, and temperature was gradually increased since then. The pattern has a good agreement with previous reconstruction, using several multi-decadal paleoclimate records by Yang et al. [2003]. By comparison, the pattern shows the similar fluctuations with solar activity on centurial scale (i.e., the “de Vries” cycle of ~200 years). Moreover, it indicates that the warmth of MWP over TP coheres with that over Northern Hemisphere and Eastern China, as well as that during the first half of 20th century. However, the LIA over TP was little warm than that in Eastern China, i.e., 17th and 19th century. Furthermore, the abrupt cold event over Northern hemisphere around 1970s was evidently recorded against the reconstruction of increasing temperature during 20th century. \nBy EOF analysis of these 15 series, it suggests that the climate anomalies during past millennium (e.g., MWP, LIA and post-industrial warming) have showed marked regional differences over sub-regions of TP. The MWP lasts until 12th century in Northeast TP, North TP and Karakoram area, while ~1450s in South TP. The duration of LIA over TP is consistent relatively (about 1450s-1870s); however, the cold epoches during LIA in Northeast TP and Western TP (~1450s-1520s, 1650s-1750s and 1780-1850s) are incompatible with them in Karakoram area (~1450s-1650s, 1740s-1780s and 1820s-1850s; among them, the warm period during 1650s-1740s is also recorded by ice cores in North TP), and the cold episodes are not evidently recorded in materials of Southern TP. Last, few tree ring chronology in South TP indicates a decrease trend of summer temperature under the background of increasing temperature recently on global scale. So, studying the inconsistency in temperature change of different seasons (i.e., summer and winter) during past millwnnium by high resolution paleoclimate records would contribute greatly to understand global warming. \nFinally, the scientific problems need to be resolved currently in the domain of climate change during past millennium over TP includes: 1), more high resolution paleoclimate series with explicit implication for climate factor; 2), new synthesized method. Especially, under the background of warm climate scenario (i.e., MWP), the influence of regional hydrological cycle over tropical ocean (i.e., the Indo-Pacific warm pool) on the Asia monsoon system would be a new research field. |
| 中文关键词 | 青藏高原 ; 近千年 ; 气候变化 ; 基本格局 ; 区域特征 ; CPS ; EOF |
| 英文关键词 | Tibet Plateau climate change past millennium general pattern spatiotemporal pattern comprehensive analysis EOF |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287109 |
| 推荐引用方式 GB/T 7714 | 张彦成. 青藏高原地区近千年气候变化时空特征的初步研究[D]. 中国科学院大学,2012. |
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