Because of the large number and remoteness, satellite data, including microwave data and optical imagery, have commonly been used in alpine glaciers surveys. Using remote sensing and Geographical Information System （...Because of the large number and remoteness, satellite data, including microwave data and optical imagery, have commonly been used in alpine glaciers surveys. Using remote sensing and Geographical Information System （GIS） techniques, the paper presents the results of a multitemporal satellite glacier extent mapping and glacier changes by glacier sizes in the Mt. Qomolangma region at the northern slopes of the middle Himalayas over the Tibetan Plateau. Glaciers in this region have both retreated and advanced in the past 35 years, with retreat dominating. The glacier retreat area was 3.23 km2 （or o.75 km^2 yr^-1 during 1974 and 1976, 8.68 km^2 （or 0.36 km^2 yr^-1 during 1976 and 1992, 1.44 km^2 （or 0.12 km^2 yr^-1） during 1992-2ooo. 1.14 km^2 （or 0.22 km^2 yr^-1 during 2000-2003, and 0.52 km^2 （or 0.07 km^2 yr^-1 during 2003-2008, respectively. While supra-glacier lakes on the debris-terminus of the Rongbuk Glacier were enlarged dramatically at the same time, from 0.05 km^2 in 1974 increased to 0.71 km^2 in 2008, which was more than 13 times larger in the last 35 years. In addition, glacier changes also showed spatial differences, for example, glacier retreat rate was the fastest at glacier termini between 5400 and 5700 m a.s.l than at other elevations. The result also shows that glaciers in the middle Himalayas retreat almost at a same pace with those in the western Himalayas.展开更多
The origin of boron in boron-rich salt lakes in the Tibetan Plateau is highly controversial.In this study,we carried out a detailed study on boron geochemistry and isotope composition of lake sediments collected in Zi...The origin of boron in boron-rich salt lakes in the Tibetan Plateau is highly controversial.In this study,we carried out a detailed study on boron geochemistry and isotope composition of lake sediments collected in Zigetang Co,central Tibet.Evaporites had high boron concentrations of 172.3–418.6 lg/g and δ^(11)B values of-8.2%to-3.3%,suggesting a non-marine origin for the saline lake.The boron isotopic fractionation factor,a,between evaporite and brackish water(a_(evaporite–brackish))decreased systematically with depth,from 0.9942 at the top of the drill core to 0.9893 at the bottom;the linear variation between α_(evaporite–brackish)and depth reflects boron isotopic fractionation associated with progressive crystallization.The positive correlation between δ^(11)B versus[B]and δ^(11)B versus depth in the evaporite phase reflects pH and boron speciation in the solution control on the adsorption of boron,and B(OH)_3 species incorporated preferentially into Mg(OH)_2 precipitation at high pH.展开更多
基金supported by the National Natural Science Foundation of China (40601056, 40121101)the Special Funds for Major State Basic Research Project (2009CB723901)+4 种基金the Special Science Foundation on Meteorological Project Research for Public Benefit (GYHY(QX)2007-6-18)the Survey Project on Glacier resources and their changes in China (No.2006FY110200)the Opening Fund projects of State Key Laboratory of Remote Sensing Science in the Institute of Remote Sensing Applicationsthe innovative project of Institute of Tibetan Plateau Research (ITPR),CASthrough a cooperation project between the Climate Change Institute, University of Maine supported by the National Oceanic and Atmospheric Administration (NA04OAR4600179) and the Institute of Tibetan Plateau Research (ITPR), CAS
文摘Because of the large number and remoteness, satellite data, including microwave data and optical imagery, have commonly been used in alpine glaciers surveys. Using remote sensing and Geographical Information System （GIS） techniques, the paper presents the results of a multitemporal satellite glacier extent mapping and glacier changes by glacier sizes in the Mt. Qomolangma region at the northern slopes of the middle Himalayas over the Tibetan Plateau. Glaciers in this region have both retreated and advanced in the past 35 years, with retreat dominating. The glacier retreat area was 3.23 km2 （or o.75 km^2 yr^-1 during 1974 and 1976, 8.68 km^2 （or 0.36 km^2 yr^-1 during 1976 and 1992, 1.44 km^2 （or 0.12 km^2 yr^-1） during 1992-2ooo. 1.14 km^2 （or 0.22 km^2 yr^-1 during 2000-2003, and 0.52 km^2 （or 0.07 km^2 yr^-1 during 2003-2008, respectively. While supra-glacier lakes on the debris-terminus of the Rongbuk Glacier were enlarged dramatically at the same time, from 0.05 km^2 in 1974 increased to 0.71 km^2 in 2008, which was more than 13 times larger in the last 35 years. In addition, glacier changes also showed spatial differences, for example, glacier retreat rate was the fastest at glacier termini between 5400 and 5700 m a.s.l than at other elevations. The result also shows that glaciers in the middle Himalayas retreat almost at a same pace with those in the western Himalayas.
基金supported by the National Basic Research Program(973 project)of China(2013CB956401)the National Natural Science Foundation of China(Grant Nos.41210004,41661144042)
文摘The origin of boron in boron-rich salt lakes in the Tibetan Plateau is highly controversial.In this study,we carried out a detailed study on boron geochemistry and isotope composition of lake sediments collected in Zigetang Co,central Tibet.Evaporites had high boron concentrations of 172.3–418.6 lg/g and δ^(11)B values of-8.2%to-3.3%,suggesting a non-marine origin for the saline lake.The boron isotopic fractionation factor,a,between evaporite and brackish water(a_(evaporite–brackish))decreased systematically with depth,from 0.9942 at the top of the drill core to 0.9893 at the bottom;the linear variation between α_(evaporite–brackish)and depth reflects boron isotopic fractionation associated with progressive crystallization.The positive correlation between δ^(11)B versus[B]and δ^(11)B versus depth in the evaporite phase reflects pH and boron speciation in the solution control on the adsorption of boron,and B(OH)_3 species incorporated preferentially into Mg(OH)_2 precipitation at high pH.
