In recent decades,the continuously changed glaciers in the Himalayas not only affected process of atmospheric flow and water cycle in the plateau but also increased the frequency of secondary disasters,such as ice col...In recent decades,the continuously changed glaciers in the Himalayas not only affected process of atmospheric flow and water cycle in the plateau but also increased the frequency of secondary disasters,such as ice collapse and outburst floods.Therefore,the monitoring of Himalayas glacial change is of great significance in the aspects of climate change and disaster prevention and reduction.The Himalayas glacier outlines in China were extracted by ratio threshold and visual interpretation based on the Landsat TM/ETM+/OLI data and glacier catalogue data.Based on the ASTER GDEM data,the distribution and change characteristics at different altitudes were studied,and the surface moraine was identified to study the influence of glacial area variations.In addition,Glaciers were divided into marine and continental glaciers in this study,and the distribution and changes of the two types of glaciers were analyzed.Also,a comprehensive analysis of a long time series was performed.The results showed that:(1)From 1990 to 2015,the glaciers in the study area showed an overall trend of melting;the annual melting speed gradually accelerated from 0.48%/a to 0.75%/a.The total melting glacial area was 828.16 km,and the melting rate of the glaciers in the western section was the highest,at 0.63%.(2)The total area of continental glaciers was larger than that of marine glaciers,and its reduction was relatively larger,too.(3)The average size of debris-covered glaciers was 10 times that of debris-free glaciers,but their rate of change(8.1%)was 1/2 of that of debrisfree glaciers(17.8%).(4)The number of glaciers gradually decreased as the size of glaciers increased.The glaciers with grades of>50 km,0.5~1 km,and 1~2 kmhad large change rates,which were 20.1%,19.1%,and 18.5%,respectively.In summary,the Himalayas glaciers in China were melting at an accelerated rate and their numbers were gradually decreasing from 1990 to 2015.The location,type,elevation,size and debris cover of a glacier are all important factors influencing glacier change.It has been found that the lower the elevation or the smaller the size of the glacier,the greater the likelihood of glacier ablation,and the debris can inhibit the melting of glaciers to a certain extent.展开更多
The relatively rapid recession of glaciers in the Himalayas and formation of moraine dammed glacial lakes(MDGLs) in the recent past have increased the risk of glacier lake outburst floods(GLOF) in the countries of Nep...The relatively rapid recession of glaciers in the Himalayas and formation of moraine dammed glacial lakes(MDGLs) in the recent past have increased the risk of glacier lake outburst floods(GLOF) in the countries of Nepal and Bhutan and in the mountainous territory of Sikkim in India. As a product of climate change and global warming, such a risk has not only raised the level of threats to the habitation and infrastructure of the region, but has also contributed to the worsening of the balance of the unique ecosystem that exists in this domain that sustains several of the highest mountain peaks of the world. This study attempts to present an up to date mapping of the MDGLs in the central and eastern Himalayan regions using remote sensing data, with an objective to analyse their surface area variations with time from 1990 through 2015, disaggregated over six episodes. The study also includes the evaluation for susceptibility of MDGLs to GLOF with the least criteria decision analysis(LCDA). Forty two major MDGLs, each having a lake surface area greater than 0.2 km2, that were identified in the Himalayan ranges of Nepal, Bhutan, and Sikkim, have been categorized according to their surface area expansion rates in space and time. The lakes have been identified as located within the elevation range of 3800 m and6800 m above mean sea level(a msl). With a total surface area of 37.9 km2, these MDGLs as a whole were observed to have expanded by an astonishing 43.6% in area over the 25 year period of this study. A factor is introduced to numerically sort the lakes in terms of their relative yearly expansion rates, based on their interpretation of their surface area extents from satellite imageries. Verification of predicted GLOF events in the past using this factor with the limited field data as reported in literature indicates that the present analysis may be considered a sufficiently reliable and rapid technique for assessing the potential bursting susceptibility of the MDGLs. The analysis also indicates that, as of now, there are eight MDGLs in the region which appear to be in highly vulnerable states and have high chances in causing potential GLOF events anytime in the recent future.展开更多
Glaciers,as“solid reservoirs”,are precious resources in arid areas.The study of glaciers is of great significance to the sustainable development and management of agriculture and the economy in northern Xinjiang.The...Glaciers,as“solid reservoirs”,are precious resources in arid areas.The study of glaciers is of great significance to the sustainable development and management of agriculture and the economy in northern Xinjiang.The area of glacier distribution on the 1963 topographic map data,1975 MSS data,2000 ETM data,2008 CBERS-2 data,2014 and 2018 ETM+were collected as secondary data.According to the remote sensing survey,the glacier areas in Northern Xinjiang are identified during 1963-2018.Based on the evolution of glacier area in the past 55 years,and using two scenarios,the average annual decrease area of a region during the whole 1963-2018 and the period with the minimum reduction area,the glacier areas of Southern Tianshan Mountains,Western Tianshan Mountains,Eastern Tianshan Mountains,the Sawuer Mountains and Altai Mountains in Northern Xinjiang,and the whole northern Xinjiang in 2030,2040,2050,and 2100 are examined and predicted.In 2100,the glacier area in Northern Xinjiang may decrease by 43%-59%.展开更多
基金funded by the National Natural Science Foundation of China(Grant Nos.41907396,42001388 and 42071277)Chongqing Research Program of Basic Research and Frontier Technology(No.cstc2019jcyj-msxm X0515)the Science Foundation of the Chongqing Normal University(22XLB002,22XLB003)。
文摘In recent decades,the continuously changed glaciers in the Himalayas not only affected process of atmospheric flow and water cycle in the plateau but also increased the frequency of secondary disasters,such as ice collapse and outburst floods.Therefore,the monitoring of Himalayas glacial change is of great significance in the aspects of climate change and disaster prevention and reduction.The Himalayas glacier outlines in China were extracted by ratio threshold and visual interpretation based on the Landsat TM/ETM+/OLI data and glacier catalogue data.Based on the ASTER GDEM data,the distribution and change characteristics at different altitudes were studied,and the surface moraine was identified to study the influence of glacial area variations.In addition,Glaciers were divided into marine and continental glaciers in this study,and the distribution and changes of the two types of glaciers were analyzed.Also,a comprehensive analysis of a long time series was performed.The results showed that:(1)From 1990 to 2015,the glaciers in the study area showed an overall trend of melting;the annual melting speed gradually accelerated from 0.48%/a to 0.75%/a.The total melting glacial area was 828.16 km,and the melting rate of the glaciers in the western section was the highest,at 0.63%.(2)The total area of continental glaciers was larger than that of marine glaciers,and its reduction was relatively larger,too.(3)The average size of debris-covered glaciers was 10 times that of debris-free glaciers,but their rate of change(8.1%)was 1/2 of that of debrisfree glaciers(17.8%).(4)The number of glaciers gradually decreased as the size of glaciers increased.The glaciers with grades of>50 km,0.5~1 km,and 1~2 kmhad large change rates,which were 20.1%,19.1%,and 18.5%,respectively.In summary,the Himalayas glaciers in China were melting at an accelerated rate and their numbers were gradually decreasing from 1990 to 2015.The location,type,elevation,size and debris cover of a glacier are all important factors influencing glacier change.It has been found that the lower the elevation or the smaller the size of the glacier,the greater the likelihood of glacier ablation,and the debris can inhibit the melting of glaciers to a certain extent.
文摘The relatively rapid recession of glaciers in the Himalayas and formation of moraine dammed glacial lakes(MDGLs) in the recent past have increased the risk of glacier lake outburst floods(GLOF) in the countries of Nepal and Bhutan and in the mountainous territory of Sikkim in India. As a product of climate change and global warming, such a risk has not only raised the level of threats to the habitation and infrastructure of the region, but has also contributed to the worsening of the balance of the unique ecosystem that exists in this domain that sustains several of the highest mountain peaks of the world. This study attempts to present an up to date mapping of the MDGLs in the central and eastern Himalayan regions using remote sensing data, with an objective to analyse their surface area variations with time from 1990 through 2015, disaggregated over six episodes. The study also includes the evaluation for susceptibility of MDGLs to GLOF with the least criteria decision analysis(LCDA). Forty two major MDGLs, each having a lake surface area greater than 0.2 km2, that were identified in the Himalayan ranges of Nepal, Bhutan, and Sikkim, have been categorized according to their surface area expansion rates in space and time. The lakes have been identified as located within the elevation range of 3800 m and6800 m above mean sea level(a msl). With a total surface area of 37.9 km2, these MDGLs as a whole were observed to have expanded by an astonishing 43.6% in area over the 25 year period of this study. A factor is introduced to numerically sort the lakes in terms of their relative yearly expansion rates, based on their interpretation of their surface area extents from satellite imageries. Verification of predicted GLOF events in the past using this factor with the limited field data as reported in literature indicates that the present analysis may be considered a sufficiently reliable and rapid technique for assessing the potential bursting susceptibility of the MDGLs. The analysis also indicates that, as of now, there are eight MDGLs in the region which appear to be in highly vulnerable states and have high chances in causing potential GLOF events anytime in the recent future.
基金jointly supported by the“Technology and Demonstration Applications for Monitoring High Snow-glacier and Geological Hazards in Asia and the Arctic”of Earth Observations Group Project Funding(2021YFE0116800)。
文摘Glaciers,as“solid reservoirs”,are precious resources in arid areas.The study of glaciers is of great significance to the sustainable development and management of agriculture and the economy in northern Xinjiang.The area of glacier distribution on the 1963 topographic map data,1975 MSS data,2000 ETM data,2008 CBERS-2 data,2014 and 2018 ETM+were collected as secondary data.According to the remote sensing survey,the glacier areas in Northern Xinjiang are identified during 1963-2018.Based on the evolution of glacier area in the past 55 years,and using two scenarios,the average annual decrease area of a region during the whole 1963-2018 and the period with the minimum reduction area,the glacier areas of Southern Tianshan Mountains,Western Tianshan Mountains,Eastern Tianshan Mountains,the Sawuer Mountains and Altai Mountains in Northern Xinjiang,and the whole northern Xinjiang in 2030,2040,2050,and 2100 are examined and predicted.In 2100,the glacier area in Northern Xinjiang may decrease by 43%-59%.
