| As an important component of the terrestrial hydrosphere,the lake is an important link connecting each layer of the surface system,and its expansion or shrinkage has an important impact on the physico-chemical characteristics of the lake and the regional environment.Lake ice is the result of energy and matter exchange at the lake-atmosphere interface,and its phenological change is of great significance for revealing regional climate change and lake response process.Under the background of global change,some lakes on the Tibetan Plateau are still expanding,and some studies show that with the change of lake area,the physical and chemical properties of lake(water clarity,mineralization)and lake ice phenology are changing significantly.With the trend of warming and humidification increasing in the future,the lake area,the variation characteristics of lake ice phenology and the response process to regional climate on the Tibetan Plateau still need to be further studied.Based on MOD09GQ,MYD09GQ and Landsat remote sensing data,combined with meteorological and lake data,GIS and RS were used to study the changes of lake area and lake ice phenological characteristics in the Selin Co Basin of the Tibetan Plateau,and the main driving factors affecting the lake ice phenology changes of the Selin Co Basin were analyzed.The results show that:(1)In the past 44 years,the total area of 21 lakes in the Selin Co Basin has increased from3495.93±14.40km~2 in 1976 to 4575.57±17.93km~2 in 2020,and the total area has expanded by 1079.64±23.36km~2,an increase of about 30.88%±0.67%.The increase of temperature and precipitation were the main driving factors of lake area expansion in Selin Co Basin.At the same time,the rising temperature of the glacier area in the basin accelerated the glacier melting,which aggravated the expansion of the lake to a certain extent.(2)The spatial patterns of lake ice freezing and melting can be classified into four types:(1)lake ice freezes from the shore to the opposite shore,and the lake ice melts earliest and the lake ice melts last;(2)Lake ice freezes from the lakeshore to the opposite shore,and deglaciation is late in the area with early ice generation.(3)Lake ice freezing extended from the sub-lake to the main lake,and the sub-lake melted together with the main lake.(4)The lake along the coast freezes first,and gradually advances to the center of the lake,the lake that freezes earlier will melt later.The spatial model of lake freezing-ablation in Selin Co Basin is influenced by lake depth,lake salinity,lake shape,ice thickness and local wind direction.(3)The lakes in Selin Co Basin began to freeze from November to December every year.After about 14 to 48 days,10 lakes were completely frozen,and 8 lakes were not completely frozen.From early March to early April,the completely frozen surface of the lake begins to melt,and from April to May,all the lake ice disappears.In the past 20 years,the freezing time of lakes in Selin Co Basin has been delayed,with an average delay rate of3.62d/10a.The total melting time of lake ice showed an earlier trend.The ice cover period was shortened with an average rate of 5.52d/10a.The ice phenology in Selin Co Basin is influenced by climatic conditions and the physico-chemical characteristics of the lake.The temperature and precipitation in the winter half-year are the key factors affecting the freezing and melting time of lake ice and the existence period of lake ice.Wind speed has a certain effect on the freezing of lake ice.The mineralization of lake water was positively correlated with the beginning freezing date of lake ice.The area of the lakes mainly affects the freeze-up dates and ice cover duration;the larger the lake area was,the later the lake began to freeze.The higher the elevation of the lake,the earlier freeze-up starts dates and the longer the ice cover period.The more complex the lake form,the earlier freeze-up start dates.The lower the water clarity of the lake,the earlier freeze-up dates,and the longer ice cover duration. |
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