【作者】 刘平；

【导师】 邬光剑； 曹泊；

【作者基本信息】 兰州大学 ， 地理学·地图学与地理信息系统， 2025， 硕士

【摘要】 青藏高原是全球中低纬地区冰川最为集中的地区之一,也是对气候变化最敏感的地区之一。在气候变暖的背景下,青藏高原地区的冰川经历了剧烈的退缩与消融,不仅对区域内水资源产生一定的影响,还会引起冰崩、冰川跃动和冰湖溃决等冰川自然灾害。过去几十年,学者普遍认为气温和降水是该地区冰川消融的主要影响因素。但是,最近研究表明,冰川反照率在能量平衡中起着主导作用,冰川表面反照率的降低会增强短波辐射吸收,从而加速冰川消融。然而,目前对青藏高原地区冰川反照率变化及其影响因素的理解仍有限,尚未系统地评估不同区域冰川反照率降低对冰川消融的贡献。因此本研究以青藏高原地区为研究区,基于遥感影像和冰川编目数据,分析了青藏高原地区2000–2022年间不同时间尺度下无表碛覆盖区冰川反照率变化。结合气象因子,黑碳和粉尘等影响因素,探讨了青藏高原地区冰川反照率变化的原因。基于增强型温度指数模型和表面高程变化数据集,模拟了2000–2020年冰川年际物质平衡,分析了气温变化和反照率降低对青藏高原地区不同区域冰川消融的影响。利用未来气候情景数据,预测了2020–2100年未来冰川反照率变化。本文初步得到的结论如下:（1）2000–2022年间青藏高原地区去除冰川表碛部分后,面积大于1.5 km²的冰川有8476条,总面积为53,107.54 km²。2000–2022年青藏高原地区冰川反照率加权均值为0.575±0.068,区域内大部分冰川反照率数值在0.5～0.6之间。反照率数值季节性差异明显,春季反照率值最高（0.654）,其次是冬季（0.610）,然后是秋季（0.558）,最后是夏季（0.516）。2000–2022年,青藏高原地区的冰川反照率呈现下降趋势,下降速率为0.06×10^-2a^-1,大部分地区呈现下降趋势,而兴都库什和西喜马拉雅由于气温降低呈现上升趋势(0.06×10^-2a^-1)。四季中,秋季冰川反照率下降的最快,为0.18×10^-2 a^-1,冬季次之(-0.06×10^-2a^-1),夏季最慢(-0.01×10^-2a^-1),而春季呈现上升趋势,为0.02×10^-2a^-1。（2）青藏高原地区不同区域冰川反照率垂直分布特征表现为:冰川反照率数值随海拔的上升而显著上升。青藏高原地区不同区域冰川反照率变化率垂直分布特征表现为:大部分地区冰川反照率的变化率与海拔呈现V型曲线关系,即随着海拔的升高,冰川反照率的下降速度会逐渐加快,直至达到某一海拔高度后反照率变化率达到最小值,随后反照率的变化率逐渐回升,反照率的下降速度放缓。其中喜马拉雅东部、横断山和藏东南等区域均呈现这种V型曲线关系。而在西喜马拉雅和喀喇昆仑等区域,由于西风带来大量水汽,增加了降雪事件,导致低海拔地区积雪覆盖增加,使得冰川反照率变化率在低海拔处是呈现上升趋势。（3）2000–2022年间,青藏高原地区冰川反照率变化受多种因素共同作用。冰川反照率与降雪的相关系数为0.61,与气温和黑碳的相关系数分别为-0.70和-0.57,而与降水和粉尘的相关性较弱,相关系数分别为0.22和0.24。从季节方面看,在春季,西喜马拉雅地区受粉尘的影响显著;在夏季,祁连山、东昆仑、青藏高原内部和喜马拉雅山西部等地区的反照率更显著地受降雪影响;在秋季,降水主要影响祁连山地区的反照率;在冬季,青藏高原内部主要受到黑碳的影响。（4）如果大气中粉尘和黑碳在本世纪仍按现有速率演变,2020–2100年间青藏高原各区域的冰川反照率在三个不同的排放情景下（SSP1-2.6、SSP2-4.5和SSP5-8.5）均呈现下降趋势。在低排放情景（SSP1-2.6）下,本世纪末青藏高原冰川反照率相较于2000–2020年的年均反照率下降约5.1%;在中等排放情景（SSP2-4.5）下,下降约7.5%;而在高排放情景（SSP5-8.5）下,冰川反照率下降幅度显著,约为12.8%。其中,喜马拉雅山和横断山地区的反照率下降幅度最大。（5）利用增强型温度指数模型,模拟得出2000–2020年青藏高原地区冰川年均物质平衡为-0.26 mw.e.,整体处于物质亏损状态。青藏高原地区冰川年均积累量和消融量分别为0.36 mw.e.和0.62 m.w.e.,与物质积累相比,冰川消融对物质平衡的影响更加显著。青藏高原地区由于气温变化引起的冰川消融量为0.35 mw.e.a^-1,占总消融量的62.2%;反照率降低导致的消融量为0.27 mw.e.a^-1,占比37.8%。从空间分布来看,西部地区（如喀喇昆仑山、帕米尔山、兴都库什山）冰川消融主要受气温变化影响,这与该地区干冷气候和较弱的太阳辐射相关;而东部地区（如横断山、唐古拉山、冈底斯山）冰川消融则以反照率降低为主导因素,这与其暖湿气候和较强的太阳辐射密切相关。由此可见,冰川消融机制呈现从西部气温主导到东部反照率主导的转变。更多还原

【Abstract】 The Tibetan Plateau is one of the regions in the world with the highest concentration of glaciers in middle and low latitudes,and it is also one of the areas most sensitive to climate change.Under global warming,glaciers in the Tibetan Plateau have experienced significant retreat and melting,affecting regional water resources and triggering glacier-related natural disasters such as ice avalanches,glacial surges,and glacial lake outburst floods.In past decades,scholars have generally considered temperature and precipitation as the primary drivers of glacier melt in this region.However,recent research indicates that glacier albedo is dominant in the energy balance.A decrease in glacier surface albedo enhances shortwave radiation absorption,thereby accelerating glacier melt.Despite these findings,our understanding of glacier albedo changes and their driving factors in the Tibetan Plateau remains limited,and the contribution of albedo reduction to glacier melting across different regions has yet to be systematically evaluated.This study focuses on the Tibetan Plateau,analyzing glacier albedo changes from 2000 to 2022 at different time scales,excluding areas covered by supraglacial debris.The analysis is based on remote sensing imagery and glacier inventory data.By integrating meteorological factors,black carbon,dust,and other influencing variables,this study investigates the reasons behind glacier albedo changes in the past 23 years.Based on the enhanced temperature index model and surface elevation change datasets,this study simulates the annual glacier mass balance from 2000 to 2020 and evaluates the impacts of temperature changes and albedo reduction on glacier melt in different regions of the Tibetan Plateau.Finally,using future climate scenario data,this study simulates glacier albedo changes from 2020 to2100.The preliminary conclusions of this study are as follows:（1）Between 2000 and 2022,after removing the influence of supraglacial debris,there were 8,476 glaciers larger than 1.5 km² in the Tibetan Plateau,with a total area of53,107.54 km².Over the past 23 years,the weighted average glacier albedo for the region was 0.575±0.068,with most glaciers exhibiting albedo values between 0.5 and0.6.The interannual variation in glacier albedo distribution was not significant,but there were distinct seasonal fluctuations.The highest albedo was observed in spring（0.654）,followed by winter（0.610）and autumn（0.558）,and the lowest in summer（0.516）.From 2000 to 2022,the glacier albedo in the Tibetan Plateau showed a decreasing trend at a rate of 0.06×10^-2 a^-1.Most regions exhibited a decline,while the Hindu Kush and Western Himalayas showed an increasing trend(0.06×10^-2 a^-1)due to decreasing temperatures.The rate of glacier albedo change varied significantly across seasons:the fastest decrease occurred in autumn(-0.18×10^-2 a^-1),followed by winter(-0.06×10^-2 a^-1),and the slowest in summer(-0.01×10^-2 a^-1);in contrast,spring showed an increasing trend(0.02×10^-2 a^-1).（2）The vertical distribution of glacier albedo in different regions of the Tibetan Plateau showed a clear pattern:albedo values significantly increased with altitude.The vertical distribution characteristics of the rate of change in glacier albedo with elevation were as follows:in most areas,the rate of change followed a V-shaped curve.As elevation increased,the rate of decline in glacier albedo initially accelerated,reaching a minimum value at a certain altitude,after which the rate of change in albedo gradually increased,and the rate of decline slowed down.This V-shaped relationship was observed in regions such as the Eastern Himalayas,Hengduan Shan,and Southeastern Tibet.However,in areas such as the Western Himalayas and Karakoram,the westerlies brought abundant moisture,leading to more snowfall events and increased snow cover at lower elevations.As a result,the rate of change in glacier albedo in these regions exhibited an upward trend at lower elevations.（3）Glacier albedo changes in the Tibetan Plateau from 2000 to 2022 were influenced by multiple factors.Albedo correlated positively with snowfall（R=0.61）and negatively with temperature and black carbon（R=-0.70 and-0.57,respectively）.The correlation with precipitation and dust was weaker（R=0.22 and 0.24）.Seasonally,the albedo in the western Himalayas was significantly influenced by dust in spring.In summer,snowfall had a more pronounced effect on glacier albedo in areas such as the Qilian Shan,East Kunlun,Inner Tibet,and the Western Himalayas.In autumn,precipitation mainly affected the albedo in the Qilian Shan.In winter,black carbon was the primary influencing factor in the Inner Tibet.（4）If dust and black carbon continue to change at their current rates throughout this century,glacier albedo across all regions of the Tibetan Plateau is projected to decline between 2020 and 2100 under three different emission scenarios:SSP1-2.6,SSP2-4.5,and SSP5-8.5.Under the low-emission scenario（SSP1-2.6）,the albedo is expected to decrease by approximately 5.1%relative to the 2000–2020 mean.In the moderate-emission scenario（SSP2-4.5）,the decrease is around 7.5%,while under the high-emission scenario（SSP5-8.5）,the decrease becomes more pronounced,at about12.8%.Among these regions,the most significant reductions in albedo are projected for the Himalayas and Hengduan Shan.（5）Using the enhanced temperature index model,the simulated annual glacier mass balance in the Tibetan Plateau from 2000 to 2020 was-0.26 mw.e.,indicating an overall mass loss.The average annual accumulation and melt were 0.36 mw.e.and 0.62mw.e.,respectively.Most mountain ranges showed decreasing mass balance trends,with the Kunlun and Altun Mountains remaining relatively stable,while the Hengduan Shan exhibited a significant decline.Glacier melt due to temperature changes amounted to 0.35 mw.e.a^-1,accounting for 62.2%of the total melt,while melt resulting from albedo reduction was 0.27 mw.e.a^-1,contributing 37.8%.Spatially,the western regions,including the Karakoram,Pamir,and Hindu Kush mountains,were primarily influenced by temperature variations,which can be attributed to the region’s cold and dry climate as well as relatively weak solar radiation.In contrast,the eastern regions,such as the Hengduan Shan,Tanggula Mountains,and Gangdise Mountains,exhibited a dominant influence of albedo reduction,closely linked to their warm,humid climate and stronger solar radiation.These findings suggest a regional transition in the glacier melt mechanism from being predominantly temperature-driven in the west to albedo-driven in the east.更多还原