Research On Lake Ice Changes In Nam Co Lake Basin And Its Response To Climate Change

Lakes which were connection point of atmosphere, biosphere, pedosphere and land hydrosphere, were complex of nature. Its formation, disappearance, expansion, contraction and the ecological environment caused by lakes were common result of global, regional and local tectonic and climatic events. Thus lakes were sensitive region to global environmental change, and Qinghai-Tibet Plateau glaciers and inland lakes were sensitive indicators of climate change. It was of great significance to carry out the change research in the Qinghai-Tibet Plateau glaciers and lakes for the study of global climate change and sustainable development.The rapid development of remote sensing and geographic information systems technology had provided technical support for lake research. This article ,in support of National Natural Science Foundation Project (40601056, 40121101), National Key Basic Research Development Program (2009CB723901), public sector (meteorology) special research "Chinese cryosphere satellite monitoring key technology research and system development" (GYHY (QX) 2007- 6-18), the opening foundation of State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing Applications, Chinese Academy of Sciences, and cutting-edge projects of Environmental Change and the surface process laboratory, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, took Nam Co as the research object to monitor lake free-thaw process using EOS/MODIS1B remote sensing data between 2005-2007 ,and some TM etc. data from 1976 of Nam Co lake, to explore remote sensing image interpretation sings and methods in lake freeze-thaw process combining computers and geographic information systems technology, analyze lakes freeze-thaw changes of study area, supply research methods for other lakes in Qinghai-Tibet Plateau . By extracting lake ice through density slicing, The main research results and conclusions of this paper were as follows:1. There were good results and strong flexibility for image information enhancement by remote sensing image digital processing. Remote sensing image processing also had a strong targeted and selective, there was a certain relevance of different treatment methods for enhancing and extracting information of different features. By a number of tests studying, it proved that using false color composite images, density slicing, combining with visual interpretation, the information extraction of Nam Co lake could be more conductive to lake ice's identification and interpretation, and reach good results.2. Research showed that, in recent decades, because of global climate warming, resource development and excessive use of human, environment had varied with degrees of change, at the same time, with the climate warming, drying, lakes and rivers runoff also fell significantly. The total area of Nam Co expanded, and the lake system correspondingly turned on series of interactive characterization affected by the impact of global warming, alpine glaciers, regional geological structure and other factors.3. Nam Co 30 years'of lake changes and climate change was in the interactionThis paper analyzed climate change near 30 years of Nam Co according to the contrast in temperature and precipitation changes characteristics of Nam Co over the past 30 years . Study showed that:â‘ The cool-season temperature change in Nam Co since 1970 turned on warming trend ,and the change was slightly;â‘¡The cool-season precipitation changes in Nam Co since 1970 increased while evaporation reduced;As temperatures rising, glaciers melt Nyainqentanglha Hill accelerated. The total area of Nam Co lake expanded because its water supply was mainly by snow and glacier melting. Lake frozen delayed in time because the temperature increased.In the long run, the total area of water and its proportion was rising in Nam Co lake during 1976-2006 12 mid to late period, correspondingly, the area of lake ice and its proportion showed a declining trend, which were directly related by temperature and precipitation increasing and evaporation decreasing during this period in Nam Co basin.Short-term research also showed that Lake ice freeze time delayed while thaw time was ahead of time in Nam Co lake, which were inseparable with climate change in over 30 years.