| 摘要: |
| 冰川与全球气候变化、水资源保护等有着密切关系。根据前人测得的嘎尔琼沟冰碛物10Be暴露年龄，以及冰川塑性流动理论重建深海氧同位素3阶段（MIS3）以来12次冰进期古冰川表面高程和厚度分布，并分别运用积累区面积比率法（accumulation area ratio，AAR）和面积-高程平衡率法（area altitude balance ratio，AABR）重新估算各期冰川作用的平衡线高程（equilibrium-line altitude，ELA）。结果显示：（1）该冰川面积从MIS3时期的18 km2减少为现在的7.5 km2，小冰期（Little Ice Age，LIA）以来锐减；（2）冰川体积从MIS3时期的1.909 km3减少为现在的0.703 km3，缩减1.206 km3；（3）ELA自MIS3以来上升296 m或227 m，MIS2早期以来上升220 m或178 m，末次冰盛期（Last Glacial Maximum，LGM）以来上升206 m或169 m，早全新世以来上升169 m或144 m，新冰期以来上升113 m或108 m，LIA以来上升79 m或85 m。通过区域对比发现，从30 ka BP开始，青藏高原总体上趋向干旱化，嘎尔琼沟冰进规模逐次减小是对干旱化气候背景的响应。新冰期研究区冰川萎缩速度加快，可能与青藏高原季风在同时期的显著减弱有关。 |
| 关键词: MIS3以来 古冰川重建 冰川体积 平衡线高程 冈底斯山 |
| DOI：10.7515/JEE192028 |
| CSTR：32259.14.JEE192028 |
| 分类号: |
| 基金项目:黄土与第四纪地质国家重点实验室开放基金（SKLLQG1836） |
| 英文基金项目:Open Fund for State Key Laboratory of Loess and Quaternary Geology (SKLLQG1836) |
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| Reconstruction past glacier since MIS3 and estimate its area, volume and equilibrium-line altitudes in Gaerqiong valley, Lunpo Gangri central Gangdese |
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WANG Youqi, ZHOU Weijian, WU Yubin
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1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. Xi’an AMS Center, Xi’an 710061, China
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| Abstract: |
| Background, aim, and scope Glaciers are closely related to global climate change and water conservation. Reconstruction of paleoglacial surface and its equilibrium-line altitude (ELA) has gradually become new hotspots. Gaerqiong valley is located in middle Gangdese, and preserved glacial landform evidence since Marine Isotope Stage 3 (MIS3). In order to learn more about the history of glaciers in the area, firstly we reconstructed paleoglacial thickness, then calculated glacial volume and finally estimated ELAs. Materials and methods According to the moraine ridges of different periods in the Gaerqiong valley and the glacial plastic flow theory, we used a series of ArcGIS scripting tools to reconstruct paleoglacier and estimated its volume. Then we used the accumulation area ratio (AAR) and area altitude balance ratio (AABR) methods to estimate the ELA of the glacial advance in each period. Results The results show that: (1) the area of the glaciers decreased from 18 km2 in the MIS3 period to the current 7.5 km2; (2) the volume of glaciers decreased from 1.909 billion m3 in the MIS3 period to the present 703 million m3, reduced by 1.206 billion m3; (3) ELA from MIS3 Since then, it has risen by 296 m or 227 m. Since early MIS2, it has risen by 220 m or 178 m. Since Last Glacial Maximum (LGM), it has risen by 206 m or 169 m. Since the early Holocene, it has risen by 169 m or 144 m. Since Neoglaciation, it has risen by 113 m or 108 m. Since the Little Ice Age (LIA), it has risen by 79 m or 85 m. Discussion Comparing the ΔELA calculated by the toe to headwall altitude ratio (THAR) method, it can be found that the results of the LGM and early Holocene are significantly different. This is because the elevation of the glacial tongue does not have a large vertical drop downstream, resulting in little change in the ΔELA of the THAR method. Conclusions Tibetan Plateau generally became arid since 30 ka BP which resulted in shrinking of Gaerqiong glacier advances. Neoglaciation was a turning point of glacial shrinking, that may be related to the significant weakening of the Tibetan Plateau monsoon during the same period. The sharp rise in greenhouse gas (such as methane) concentrations and temperatures since the Industrial Revolution is a key factor in the rapid shrinkage of the LIA glacier. Recommendations and perspectives The reconstruction of paleoglacial is difficult job, but it is of great significance for our understanding the Quaternary glacial changes with the development of computer technique and the improvement of glacial dynamics models, we will be able to reconstruct more accurate paleoglacial picture. |
| Key words: since MIS3 glacial ice volume paleoglacial ELA Gangdese |
