青藏高原湖泊面积动态监测

高原湖泊的动态变化对区域水循环具有重要影响。受全球气候变化的影响,青藏高原湖泊自20世纪90年代开始呈现剧烈扩张趋势。为揭示近年来青藏高原湖泊面积的时空变化规律,本文提出了一种改进的半自动湖泊提取算法,结合环境减灾卫星（HJ-1A/1B）和Landsat系列卫星影像数据,对青藏高原内流流域中面积大于50 km²的127个湖泊进行了连续6年的动态监测,并分析了该区域2009-2014年湖泊面积时空变化特征。研究结果表明,该区域湖泊整体呈现显著扩张趋势,年均变化速率为231.89 km²yr^-1（0.87 %yr^-1）,6年间湖泊面积扩张速率有所减缓。其中,扩张湖泊有104个,收缩湖泊有23个,变化速率分别为271.08 km²yr^-1（1.02 % yr^-1）和-39.19 km²yr^-1（-0.15 %yr^-1）。不同区域湖泊面积变化具有明显差异,主要表现为东部及北部大部分区域湖泊扩张,南部地区大部分湖泊面积稳定,萎缩湖泊主要分布于研究区四周。最后,本文通过分析冰川融水补给对湖泊面积变化的影响,发现存在冰川融水补给的湖泊面积变化率远大于不存在冰川融水补给的湖泊。由此可见,近年来冰川融水的增加是促进青藏高原内流流域湖泊扩张的主要因素之一。

Spatiotemporal Monitoring of Lake Area Dynamics on the Tibetan Plateau

The lakes on the high-altitude plateau play an essential role in the local water cycle. Alpine lakes on the Tibetan Plateau have experienced a rapid expansion since 1990s under the global climate change. In order to understand the changing pattern of alpine lakes on the Tibetan Plateau in recent years, this study monitored 127 lakes larger than 50 square kilometers annually on the endorheic Tibetan basin from 2009 to 2014. Based on a semi-automatic lake extraction method, we combined multi-temporal HJ-1A/1B imagery and Landsat imagery to extract lake boundaries accurately. The results have shown that the surface area of large lakes experienced a significant expansion with an overall rate of 231.89 km² yr^-1 (0.87 %yr^-1) and the trend of lake expansion is slowing down during the study period. 104 lakes expanded at a rate of 271.08 km² yr^-1 (1.02 %yr^-1), while 23 lakes shrunk at a rate of -39.19 km² yr^-1 (-0.15 %yr^-1). The spatial pattern of the lake area dynamics also have shown significant regional difference. The expanded lakes are distributed in the most of the east and north study area, while the stable lakes are mainly distributed in the south basin. Besides, the shrunken lakes are scattered at the border of the study area. Based on the comparison between the changing rates of glacier-fed and non-glacier-fed lakes, glacier-fed lakes have shown a much rapid expansion trend than non-glacier-fed lakes, which indicates that the increase of glacier wastage is one of the main factors that contributed to the expansion of Tibetan lakes.