Changes in Glacial Lakes in Naqu from 1990 to 2020

Due to global warming and retreat of glaciers in recent years, the number and total area of glacial lakes in Qinghai-Tibet Plateau have increased rapidly, leading to increased frequency of glacial lake outburst floods (GLOF), threatening people’s property and livelihood in downstream regions．Remote sensing images from Landsat were subject to visual interpretation, to obtain the boundary of glacial lakes and glaciers in Naqu in 1990, 2000, 2010 and 2020．Characteristics and reasons for change in glacial lakes in Naqu in the past 30 years were then analyzed．A total of 255 glacial lakes were identified in Naqu, with a total area of (27.83 ± 4.62) km²．Glacial lakes were concentrated in the southeast and southwest of Naqu．Noticeable expansion of glacial lakes was found from 1990-2020, total number of glacial lakes increased by 72, and total surface area increased by 6.14 km²．Original glacial lakes expanded rapidly in the low altitude region (≤4700 m), newer glacial lakes were distributed in high altitude area (>5100-5700 m)．Temperature and precipitation were critical factors in the expansion of glacial lakes．Due to spatial and temporal differences in temperature and precipitation in Naqu, expansion of glacial lake was faster in the south, compared to the north, expansion rate of the whole region accelerated gradually．The location of glacial lakes could also affect the process of expansion．A closer distance of a glacial lake to the glacier favors its development．Glaciers connected to lakes shows higher melting rate．No evidence was found for a linear relationship between glacier and glacial lake area change．