利用VOLTA模型估算西藏卡鲁雄峰地区现代冰川的规模

Estimations of glacial thickness and volume in Mt. Kaluxung region of Qinghai-Xizang Plateau using VOLTA model

关键词:  青藏高原  卡鲁雄峰地区  现代冰川  冰川规模估算  冰厚分布  VOLTA模型

Key words:  Qinghai-Xizang Plateau  Mt. Kaluxung region  modern glaciers  glacier scale estimation  ice thickness  VOLTA model

摘要:

作为气候变化的敏感指示器，青藏高原地区的部分冰川正经历着显著而持续的消融，这将导致流域地表径流改变、地质灾害发生风险增加，甚至区域自然环境恶化。因此，查明青藏高原地区现代冰川规模具有重要意义。以西藏卡鲁雄峰地区为代表性研究区域，采用冰量模型（volume and topography automation，VOLTA）模拟冰厚分布并估算冰储量。结果显示：研究区冰川总面积约26.197 km²，冰储量约0.828 km³（误差在−16.6%—26.6%），大部分区域冰厚在50 m以下，最大冰厚约218 m，平均厚度约32 m。此外，还比较了VOLTA模型与传统的反距离权重法及经验公式法所得结果之间的差异。使用积累区面积比率法（accumulation area ratio，AAR）得到研究区面积大于0.22 km²的21条冰川的物质平衡线高度约位于5763—6275 m（误差约为15 m）。

Abstract:

Background, aim, and scope Glacier is a sensitive indicator of climate change. Under global warming, glaciers on the Qinghai-Xizang Plateau have experienced significant shrinkage, leading to risks of river runoff, geological disaster, and degradation of regional ecosystems. Investigating the spatial extent and volume of modern glaciers on the Qinghai-Xizang Plateau is thus critical for assessing regional environment response to climatic shifts. However, field-based measurements of glacier thickness remain limited due to logistical challenges. This study simulates glacier thickness distribution, ice volume, and equilibrium-line altitude (ELA) for glaciers in the Mt. Kaluxung region on the southern Qinghai-Xizang Plateau, aiming to supplement foundational data for the region. Also, we evaluate the applicability and accuracy of the volume and topography automation (VOLTA) model by comparing it with alternative methods and prior studies. Materials and methods Based on modern glacier outlines and digital elevation model (DEM), the VOLTA model is used to simulate ice thickness distribution and ice volume in the Mt. Kaluxung region. Results are cross-validated using the inverse distance weighting (IDW) method and empirical formula. The equilibrium-line altitudes (ELAs) are calculated for 21 glaciers using the accumulation area ratio (AAR) method. Results Modern glaciers in the Mt. Kaluxung region cover an area of 26.197 km², with 66.67% of the glaciers being smaller than 0.5 km². The regional average ice thickness is 32 m and the maximum ice thickness reaches 218 m, while the ice thicknesses in most parts of the study area are less than 50 m. Regional ice volume is estimated to be about 0.828 km³. The ELAs for the 21 glaciers (each with an area over 0.22 km²) range from 5763 m to 6275 m, with a calculation error of 15 m. Discussion By comparing with the records of the second glacier inventory dataset of China, our visual interpretation indicates a 7.49% (about 2.122 km²) reduction in regional glacial area, attributable to climatic forcing and/or the accuracy of the remote sensing images. Discrepancies between VOLTA and IDW-derived ice thickness distributions stem from the methods themselves: VOLTA uses ANUDEM (authorized digital elevation model) interpolation to generate spatially continuous thickness across glacierized areas; whereas IDW assumes zero thickness at glacier boundaries, amplifying result variability. Regional total ice volume estimated by the empirical formula is larger than the results calculated from the VOLTA and IDW-simulated thickness distribution. Previous studies also indicated substantial uncertainties in empirical ice volume estimation. Inter-study differences in simulated ice volume and thickness in Mt. Kaluxung may arise from inconsistencies in DEM datasets, model processing targets and manual delineation of flowline. Conclusions Glacier retreat is prominent in the study area. Compared with previous studies, the simulation results by VOLTA are affected by the features of flowlines and the difference between model processing objects. Recommendations and perspectives It is necessary to select appropriate method for ice thickness simulation based on individual glacier characteristics. The results provide critical database for water resource assessment, glacier hazard forecasting, and palaeoglacier reconstruction in the region.