Lake ice phenology variations and influencing factors of Selin Co from 2000 to 2020

Abstract

湖冰作为湖泊-大气界面能量和物质交换的结果，其物候变化对揭示区域气候变化和湖泊响应过程具有重要意义.本研究基于2000-2020年色林错边界矢量数据、Terra MODIS和Landsat TM/ETM+/OLI遥感影像并结合气象数据及湖泊资料，利用RS和GIS手段综合分析了色林错湖冰物候变化特征及其影响因素.结果表明：①色林错于11月下旬到12月上旬开始冻结，在12月下旬到1月上旬完全冻结，封冻时间约一个月左右.湖冰在每年的3月下旬到4月上旬开始消融，历经半个月左右，至4月下旬完全消融.②近20 a来，色林错开始冻结日期整体呈现逐渐推迟的波动趋势，推迟率约为11.3 d/10 a.湖冰冻结期呈缩短趋势；湖冰存在期整体上呈缩短趋势，缩短率为13.5 d/10 a.③色林错冻结先从北部和东部湖岸处开始逐渐向中部湖心处扩张，解冻时湖冰中心先破裂，向湖岸边逐渐消融.④色林错湖冰物候受气候和湖泊自身理化性质综合影响.冬半年平均气温是影响湖冰消融和封冻期的关键因素；风速和降水对湖冰的冻结和消融亦有一定影响.近20 a来，随着色林错面积扩张、浑浊度上升及透明度下降，湖冰开始冻结时间推迟，湖冰封冻期缩短.全球变暖背景下，包含色林错在内的青藏高原湖泊有加速扩张趋势，本研究结果可为理解变化环境下湖冰物候信息的气候指示意义及湖泊反馈过程提供参考.;As a result of energy and material exchange at the lake-atmosphere interface, the variations of lake ice phenology are of great significance for indicating regional climate change and lake response process. Based on the boundary data of Selin Co, some multi-source remote sensing (RS) datasets including Terra MODIS and Landsat TM/ETM+/OLI product, combined with meteorological records and lake data to analyze spatiotemporal variations of ice phenology of Selin Co and its relationship with climate factors and physical and chemical factors between 2000 and 2020 by applying both RS and GIS technology. The main research conclusions are as follows:(1) Freeze-up start (FUS) and freeze-up end (FUE) of lake ice appears in late November-early December, and late December-early January, respectively. The duration of lake ice freeze-up is about a month. The time of break-up start (BUS) and break-up end (BUE) of lake ice appears in late March-early April, and late April, respectively. The duration of lake ice break-up is about half a month. (2) Data show that FUS dates of lake ice have been delayed at a rate of 11.3 d/10 a from 2000 to 2020. FUD (freeze-up duration) time of lake ice showed an increasingly shortening trend. Ice cover duration had been shortened at a rate of 13.5 d/10 a. (3) Selin Co can be characterized by opposite spatial patterns in both freeze-up and break-up processes. Lake ice freezes from the northern and eastern lakeshore and gradually expands to the center of lake. Instead, lake ice break-up begins in the center of the lake. (4) Ice phenology of Selin Co is influenced by climate and physico-chemical factors of the lake itself. The average temperature of winter half-year (between November and the following April) plays a dominant role in ice phenology variations of Selin Co. Wind speed and precipitation both also some influences on the formation and melting of lake ice cover and also cannot be neglected. In the recent 20 years, with the expansion of Selin Co area, the increase of turbidity and the decrease of water clarity, the freezing dates of lake ice were gradually delayed. Under the background of global warming, the area expansion of lakes on the Tibetan Plateau, including Selin Co, has accelerated. The results of this study can provide a reference for understanding the climate indicator significance of lake ice phenology information and the feedback process of lakes under the changing environment.