| Climate change is a major issue the world faces today, the impact of global warming as a prominent symbol of global environmental change and its possible ecological systems and human society, and has attracted the great concern of scientists, governments and the community. There is no doubt that, since the late 19 th century, the global average surface temperature(GMST) continued to rise. Over the past three decades were warmer than any year since the meteorological data, which is ten years since 2000 the warmest decade ever. Compared to the temperature changes, the overall global land surface precipitation changes are not large, 30° ~ 60°N precipitation increases more obvious. Regionally, Northwest China gradually changes from warm-dry to warm-humid. As an important part of the terrestrial hydrosphere, lakes and its waters change are their overall results of in the basin water balance, and are sensitive indicators of climate change. Deep in the hinterland of Tibetan Plateau, the Hoh Xil region is highland lakes area of the highest elevation on Earth and the largest number, and a total area of more than 1.0 km2 lake is 1055, accounting for 39.2% and 51.4% of the total number and the total area of the lake respectively. Research shows that nearly 50 years with an average annual temperature of the Tibetan plateau increases at a rate of 0.37 ℃·10a-1, and precipitation increases at a rate of 9.1 mm·10a-1. However, the Hoh Xil region is the lack of observational data about lakes, lake levels and lake ice conditions are blank, only a few scholars have studied lakes area changes in this region. For less than the above studies, lakes of the Hoh Xil region for the study in this paper, based on topographic maps, multi-source remote sensing data, Institute of Tibetan Plateau comprehensive scientific expedition field survey data and meteorological data, and the integrated use of RS and GIS technology, we extracted lake area information in Hoh Xil region, the water level information and ice conditions. Exploring the spatial and temporal characteristics of the Tibetan plateau lakes change about a wide range of lakes and exploring its changes of its response to climate change, and dynamic changes of the lake so as to establish a new method, providing a new basis for Plateau other lakes, and providing new ideas for building Lakes dynamic changes in response to global change models. Through the study of this article, the main conclusions are as follows:(1) From the 1970 s to 2011, the lakes in the Hoh Xil region firstly shrank and then expanded. In particular, the area of lakes generally decreased during the 1970s~1990s. Then the lakes expanded during the 1990s~2000 and their area was slightly higher compared with the 1970 s.The area of lakes dramatically increased after 2000; From 2000 to 2011, the lakes with different area scales in the Hoh Xil region showed an overall expansion trend. Meanwhile, some regional differences were also discovered. Most of the lakes expanded and were widely distributed in the northern, central and western parts of the region. Some lakes merged together or overflowed due to their rapid expansion. A small number of lakes with the trend of area decrease or strong fluctuation were scattered in the central and southern parts of the study area. And their variations were related to their own supply conditions or hydraulic connection with the downstream lakes or rivers; The increase in precipitation was the dominant factor resulting in the expansion of lakes in the Hoh Xil region. The secondary factor was the increase in melt water from glaciers and frozen soil due to climate warming.(2) There are 17 lakes have only one altimeter data, 3 lakes level with a downward trend(high confidence), 17 lakes level with a rise trend(high confidence). Although a large part of the lakes no altimeter data or incomplete altimeter data, but it is not enough to cover up the Hoh Xil region generally lake level increased facts. Lake level and area has a good linear relationship, the magnitude of lake level changes and lake area scale has a negative relationship, and this relationship with the increases of the lake scale become more apparent. In Hoh Xil region, there are 18 lakes water volume increased obtained by the empirical formula used ICESat/GLAS data, while 6 lakes water volume decreased and only 1 lake water volume did not change; The inconsistent with the data time of lake area and lake level may be the reason for the reduction of the lake water fitting in this period.(3) The time of freeze-up start(FUS) and freeze-up end(FUE) of lake ice appear in the late October-early November, mid-November-early December, respectively. The duration of lake ice freeze-up is about half a month. The time of break-up start(BUS) and break-up end(BUE) of lake ice are relatively dispersed, and appear in the early February-early June, early May-early June, respectively. The ice duration(ID) and the complete ice duration(CID) of lakes are 196 days and 181 days, respectively; The phenology of lake ice in the Hoh Xil region changed dramatically in the last 10 years. Specifically, the FUS and FUE time of lake ice showed an increasingly delaying trend. In contrast, the BUS and BUE time of lake ice presented an advance. This led to the reduction of the ID and CID of lake ice. The average rates of ID and CID were-2.21 d/a and-1.91 d/a, respectively; The variations of phenology and evolution of lake ice are a result of local and climatic factors. The temperature, lake area, salinity and shape of the shoreline are the main factors affecting the phenology of lake ice. However, the other factors such as the thermal capacity and the geological structure of lake should be not ignored as well; The spatial process of lake ice freeze-up is contrary to its break-up process. The type of lake ice extending from one side of lakeshore to the opposite side is the most in the Hoh Xil region. |
PDF Full Text Request