| 摘要: |
| 小冰期出现的寒冷气候波动，促使全球范围内多处冰川再次扩张。青藏高原上保留有丰富的小冰期冰川地貌证据，利用这些地貌证据模拟古冰川规模，并重建古气候，可为了解区域水资源储量演化以及古气候特征提供重要理论支撑。采用纵剖面模型定量重建西藏廓琼岗日峰周边7条山谷内小冰期冰川规模，计算古冰川面积范围约为0.90—4.15 km2，冰储量范围约为4.28×107—2.85×108 m3，各冰川平均冰厚值范围约在31.78—99.21 m。计算小冰期与现代冰川物质平衡线高度，得到小冰期冰川物质平衡线高度约在5613—5737 m，现代冰川物质平衡线高度约在5685—5822 m。根据平衡线高度平均上升55 m的变化，结合孢粉数据显示的小冰期与现代年降水量差异，采用P-T和LR模型重建古气候，结果表明小冰期夏季平均气温比现代低0.43—0.46 ℃。 |
| 关键词: 廓琼岗日峰 小冰期 纵剖面模型 古冰川规模 古气候 |
| DOI：10.7515/JEE222093 |
| CSTR： |
| 分类号: |
| 基金项目:国家自然科学基金项目（42071002） |
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| Reconstruction of Little Ice Age glaciers and paleoclimate around the Kuoqionggangri Peak, Xizang |
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SUN Yaqing1, 2, XU Xiangke1*
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1. State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
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| Abstract: |
| Background, aim, and scope Climate fluctuations during the Little Ice Age (LIA) triggered glacier expansions worldwide. The Qinghai-Xizang Plateau preserves abundant geomorphic evidence of LIA glacier expansions, such as in the Kuoqionggangri Peak region, located in the southern Qinghai-Xizang Plateau near the western Nyainqentanglha Range. However, the extent of LIA glaciers around the Kuoqionggangri Peak remains unclear, and our understanding of the regional LIA climate is still limited. This study aims to reconstruct the LIA glacier extent using geomorphic evidence and to infer LIA climate conditions in the Kuoqionggangri Peak region. The findings provide valuable theoretical insights into the evolution of regional glacier water resources and paleoclimate characteristics on a regional scale. Materials and methods By the aid of Google Earth and ArcGIS 10.7 software, this study employs the Glacier Longitudinal Profile Model to reconstruct the extent of LIA glaciers in the study area. The equilibrium-line altitude (ELA) was determined using the accumulation area ratio (AAR), area-altitude balance ratio (AABR), and toe-to-headwall altitude ratio (THAR) methods for seven LIA glaciers and twelve modern glaciers in the corresponding valleys. Based on changes in ELA (ΔELA) between LIA and modern glaciers, along with lacustrine pollen data, the paleoclimate was reconstructed using the precipitation-temperature (P-T) empirical regression model and the temperature lapse rate (LR) model. Results (1) The area of the seven LIA glaciers in the study region ranges from 0.90 to 4.15 km2, with ice volume between 4.28×107 and 2.85×108 m3. The average surface elevation of the glaciers ranges from 5473.61 to 5805.58 m, and the average ice thickness varies between 31.78 and 99.21 m. (2) The ELA of seven LIA glaciers ranges from 5613 to 5737 m, while the ELA of twelve modern glaciers spans from 5685 to 5822 m. This represents an ELA increase by 11 to 111 m, with an average change of approximately 55 m. (3) According to the results from the P-T and LR models, the average summer temperature during the LIA was 0.43—0.46 ℃ lower than at present. Discussion By comparing the reconstructed seven LIA glaciers, it was found that LIA glacier 1 was the largest one, with topography playing a significant role in shaping the glacier size. Additionally, the presence of basal moraine on glacier bed introduced an error in the model reconstruction, resulting in a slightly smaller ice thickness value compared to the actual value. For nearby glaciers with different ELA results, this study suggests that the ELA discrepancy is due to variations in the average elevation of the valleys where the glaciers are situated, as well as the influence of topography on glacier accumulation. The valleys with ΔELA values lower than the average ΔELA for the entire region are primarily on the southeast side of the Kuoqionggangri Peak, which may be related to the amount of water vapor transported by the Indian Monsoon. When reconstructing the climate of the LIA in the study area, the results by the P-T model have an uncertainty of ±0.20 ℃, and the LR model have an uncertainty of ±0.19 ℃ in its results. Based on the combined results of temperature and precipitation during the LIA, as fitted by the model, both the changes in summer temperature and annual precipitation are small. This corresponds to the presence of reconstructed small glaciers in the study area and is consistent with previous simulations using other methods. Conclusions The scale of the LIA glaciers around the Kuoqionggangri Peak is relatively small, with LIA glacier 1 being the largest. Compared to the ELA of modern glaciers, the average ΔELA is only a few tens of meters. The simulation results indicate that the average summer temperature during the LIA was 0.43—0.46 ℃ lower than at present, which lends the findings a certain degree of credibility. Recommendations and perspectives Analyzing the sensitivity of glaciers around Kuoqionggangri Peak to climate change is crucial for understanding their response within the interaction zone of the Westerlies and the Southwest Monsoon on the Qinghai-Xizang Plateau. This study provides valuable insights into the dynamics of glacial evolution in a region influenced by complex climatic interactions. |
| Key words: Kuoqionggangri Peak Little Ice Age Longitudinal Profile Model paleoglacier scale paleoclimate |
