Glaciers in the Yarlung Zangbo Downstream Basin(YZDB) are sensitive to global climate change. The equilibrium-line altitude(ELA) is a key indicator of glacial development.Current models for simulating the meteorologic...Glaciers in the Yarlung Zangbo Downstream Basin(YZDB) are sensitive to global climate change. The equilibrium-line altitude(ELA) is a key indicator of glacial development.Current models for simulating the meteorological ELA underestimate the extent of glacial advance during the Last Glacial Maximum(LGM) in the YZDB and cannot explain the large-scale glacial extension compared with the Yarlung Zangbo Midstream Basin(YZMB). In this study, the distribution of ELA in the LGM is reconstructed using high-resolution 80-km ECHAM5 simulations and empirical relationships between temperature and precipitation.Changes in ELA between the LGM and pre-industrial era(PI) are compared. Our simulated ELA closely fits the published field data. In the YZDB, simulated LGM ELAs range from ca.3500 m to over 4900 m, representing declines of ca. 300–950 m. The ECHAM5 simulations better reflect the complex topographic features than most coarse-resolution climate models,and the ELA distribution is controlled by the spatial arrangement of river valley systems and mountain ranges and their impact on precipitation. Compared with the PI era, most of the monsoon precipitation in the LGM was concentrated in the YZDB, which is the main driver of glacial extension and the differential response of the downstream and midstream basins.展开更多
Mass balance is a key indicator of the sensitivity of glaciers to climate change. Field measurement is one of the most important ways to study the mass balance of glaciers. Based on observations of mass balance in the...Mass balance is a key indicator of the sensitivity of glaciers to climate change. Field measurement is one of the most important ways to study the mass balance of glaciers. Based on observations of mass balance in the ablation zone of Shuiguan Glacier No.4, Qilian Mountains, China, combined with the balance ratio between accumulation and ablation, we established a linear relation between mass balance and altitude. The results show that the mean annual mass balance of this glacier was ~510 mm w.e. from 2010 to 2013. The uncertainty in the balance ratio value does not lead to a significant difference in the mass balance. The equilibrium-line altitude rose by 180 m from 1972 to 2013, while the accumulation–area ratio decreased from 0.68 to 0.25. These variations may be caused by changes in air temperature. Meanwhile, the glacier is at present not in a steady state, and it may continue to shrink by a further ~900 m, even without further climate warming. In the western Lenglongling Mountains, assuming that the glaciers are in a steady state and the Equilibrium-line altitudes(ELAs)remain similar, there will be only 46 glaciers left, covering a total area of 19.2 km^2, in other words, only 22.3% of the glaciers area in 1972.展开更多
In the context of global warming,glaciers in the Asian High Mountains(AHMs)are shrinking at an accelerating rate.Projecting their future change is helpful for understanding the hydrological and climatic effects relate...In the context of global warming,glaciers in the Asian High Mountains(AHMs)are shrinking at an accelerating rate.Projecting their future change is helpful for understanding the hydrological and climatic effects related to glacier retreat.Here,we projected glacier change in the AHMs from 1979 to 2100 under shared socioeconomic pathway(SSP)scenarios from the perspective of temperature,equilibrium-line altitude(ELA),and accumulation area.The annual mean temperature in the AHMs increased by 1.26℃ from 1979 to 2014,corresponding to an increase of 210 m in the mean ELA and a decrease of 1.7×10^(4)km^(2) in the glacier accumulation area.Under the SSP2-4.5(SSP5-8.5)scenario,the annual mean temperature in the AHMs would increase by 2.84℃(3.38℃)in 2040–2060 relative to that in 1850–1900,leading to the mean ELA reaching an elevation of5661 m(5777 m).The accumulation area in the AHMs decreased by 46.3%from 1995 to 2014 and was projected to decrease by60.1%in 2040–2060.Moreover,the annual mean temperature in the AHMs was projected to increase by 3.76℃(6.44℃)in2080–2100 relative to that in 1850–1900,corresponding to the ELA reaching an elevation of 5821 m(6245 m)and the accumulation area decreasing to 1.8×10^(4)km^(2)(0.5×10^(4)km^(2)).These data suggest that the conditions for glacier development will disappear in most of the AHMs,except for extreme high-altitude regions in the Tianshan,Pamir,and Himalaya Mountains.Under the SSP2-4.5(SSP5-8.5)scenario,when the global mean temperature increases 1.5℃(2℃)above pre-industrial levels,the annual mean temperature will increase by 2.12℃(2.86℃)and the accumulation area will decrease by 15%(48%)in the AHMs compared with that in 1995–2015.Therefore,a 1.5℃ increase in global warming would keep 40%more of the glacial accumulation area(1.5×10^(4)km^(2))in the AHMs compared to a 2℃ increase in global warming.展开更多
In this paper, a collocation technique with the modified equilibrium on line method （ELM） for imposition of Neumann （natural） boundary conditions is presented for solving the two-dimensional problems of linear ela...In this paper, a collocation technique with the modified equilibrium on line method （ELM） for imposition of Neumann （natural） boundary conditions is presented for solving the two-dimensional problems of linear elastic body vibrations. In the modified ELM, equilibrium over the lines on the natural boundary is satisfied as Neumann boundary condition equations. In other words, the natural boundary conditions are satisfied naturally by using the weak formulation. The performance of the modified version of the ELM is studied for collocation methods based on two different ways to construct meshless shape functions： moving least squares approximation and radial basis point interpolation. Numerical examples of two-dimensional free and forced vibration analyses show that by using the modified ELM, more stable and accurate results would be obtained in comparison with the direct collocation method.展开更多
基金The Second Tibetan Plateau Scientific Expedition and Research Program (STEP),No.2019QZKK0902Key Research and Development Program of Xizang Uygur Autonomous Region,No.XZ202301ZY0039GNational Natural Science Foundation of China,No.42305178, No.91747207, No.41790434。
文摘Glaciers in the Yarlung Zangbo Downstream Basin(YZDB) are sensitive to global climate change. The equilibrium-line altitude(ELA) is a key indicator of glacial development.Current models for simulating the meteorological ELA underestimate the extent of glacial advance during the Last Glacial Maximum(LGM) in the YZDB and cannot explain the large-scale glacial extension compared with the Yarlung Zangbo Midstream Basin(YZMB). In this study, the distribution of ELA in the LGM is reconstructed using high-resolution 80-km ECHAM5 simulations and empirical relationships between temperature and precipitation.Changes in ELA between the LGM and pre-industrial era(PI) are compared. Our simulated ELA closely fits the published field data. In the YZDB, simulated LGM ELAs range from ca.3500 m to over 4900 m, representing declines of ca. 300–950 m. The ECHAM5 simulations better reflect the complex topographic features than most coarse-resolution climate models,and the ELA distribution is controlled by the spatial arrangement of river valley systems and mountain ranges and their impact on precipitation. Compared with the PI era, most of the monsoon precipitation in the LGM was concentrated in the YZDB, which is the main driver of glacial extension and the differential response of the downstream and midstream basins.
基金financially supported by the Ministry of Science and Technology of the People’s Republic of China (No. 2013FY111400)National Natural Science Foundation of China (No.41471008+1 种基金 No. 41571003)Fundamental Research Funds for the Central Universities (lzujbky-2015-126)
文摘Mass balance is a key indicator of the sensitivity of glaciers to climate change. Field measurement is one of the most important ways to study the mass balance of glaciers. Based on observations of mass balance in the ablation zone of Shuiguan Glacier No.4, Qilian Mountains, China, combined with the balance ratio between accumulation and ablation, we established a linear relation between mass balance and altitude. The results show that the mean annual mass balance of this glacier was ~510 mm w.e. from 2010 to 2013. The uncertainty in the balance ratio value does not lead to a significant difference in the mass balance. The equilibrium-line altitude rose by 180 m from 1972 to 2013, while the accumulation–area ratio decreased from 0.68 to 0.25. These variations may be caused by changes in air temperature. Meanwhile, the glacier is at present not in a steady state, and it may continue to shrink by a further ~900 m, even without further climate warming. In the western Lenglongling Mountains, assuming that the glaciers are in a steady state and the Equilibrium-line altitudes(ELAs)remain similar, there will be only 46 glaciers left, covering a total area of 19.2 km^2, in other words, only 22.3% of the glaciers area in 1972.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(Grant No.2019QZKK0201)the National Natural Science Foundation of China(Grant No.41571062)。
文摘In the context of global warming,glaciers in the Asian High Mountains(AHMs)are shrinking at an accelerating rate.Projecting their future change is helpful for understanding the hydrological and climatic effects related to glacier retreat.Here,we projected glacier change in the AHMs from 1979 to 2100 under shared socioeconomic pathway(SSP)scenarios from the perspective of temperature,equilibrium-line altitude(ELA),and accumulation area.The annual mean temperature in the AHMs increased by 1.26℃ from 1979 to 2014,corresponding to an increase of 210 m in the mean ELA and a decrease of 1.7×10^(4)km^(2) in the glacier accumulation area.Under the SSP2-4.5(SSP5-8.5)scenario,the annual mean temperature in the AHMs would increase by 2.84℃(3.38℃)in 2040–2060 relative to that in 1850–1900,leading to the mean ELA reaching an elevation of5661 m(5777 m).The accumulation area in the AHMs decreased by 46.3%from 1995 to 2014 and was projected to decrease by60.1%in 2040–2060.Moreover,the annual mean temperature in the AHMs was projected to increase by 3.76℃(6.44℃)in2080–2100 relative to that in 1850–1900,corresponding to the ELA reaching an elevation of 5821 m(6245 m)and the accumulation area decreasing to 1.8×10^(4)km^(2)(0.5×10^(4)km^(2)).These data suggest that the conditions for glacier development will disappear in most of the AHMs,except for extreme high-altitude regions in the Tianshan,Pamir,and Himalaya Mountains.Under the SSP2-4.5(SSP5-8.5)scenario,when the global mean temperature increases 1.5℃(2℃)above pre-industrial levels,the annual mean temperature will increase by 2.12℃(2.86℃)and the accumulation area will decrease by 15%(48%)in the AHMs compared with that in 1995–2015.Therefore,a 1.5℃ increase in global warming would keep 40%more of the glacial accumulation area(1.5×10^(4)km^(2))in the AHMs compared to a 2℃ increase in global warming.
文摘In this paper, a collocation technique with the modified equilibrium on line method （ELM） for imposition of Neumann （natural） boundary conditions is presented for solving the two-dimensional problems of linear elastic body vibrations. In the modified ELM, equilibrium over the lines on the natural boundary is satisfied as Neumann boundary condition equations. In other words, the natural boundary conditions are satisfied naturally by using the weak formulation. The performance of the modified version of the ELM is studied for collocation methods based on two different ways to construct meshless shape functions： moving least squares approximation and radial basis point interpolation. Numerical examples of two-dimensional free and forced vibration analyses show that by using the modified ELM, more stable and accurate results would be obtained in comparison with the direct collocation method.
