Ice shelves are important passageways for ice sheets flowing into the ocean.Through iceberg calving and basal melting,ice shelves exert considerable influence on the mass balance of the Antarctic Ice Sheet and glacier...Ice shelves are important passageways for ice sheets flowing into the ocean.Through iceberg calving and basal melting,ice shelves exert considerable influence on the mass balance of the Antarctic Ice Sheet and glacier stability.The Ross Ice Shelf(RIS),the largest body of floating ice on Earth,plays an essential role in any changes in the mass balance of the Antarctic Ice Sheet.The long-term elevation change trend of RIS has been calculated with multiple satellite altimetry in previous studies.However,the seasonal variations were less revealed.Based on crossover analysis and indirect observation adjustments,this study proposed a new method for constructing seasonal records for surface elevation changes in the RIS using ICESat laser altimetry data from 2003 to 2009.The results showed that surface elevation changes exhibited seasonal variations with fluctuations over 20 cm,and the seasonal change characteristics were closely related to the temperature.Interannual variations in RIS surface elevation decreased from 2003 to2009 at a rate of 2 cm/yr.From March 2003 to April 2007,the surface elevation decreased at 3.7 cm/yr;however,after April 2007,the surface elevation increased at 5.5 cm/yr.The more recent stages of surface elevation growth have been influenced by reductions in the summer basal melt,which is related to the decreases in ocean heat content.展开更多
Elevation change monitoring of the Antarctic ice sheet has been a key issue in global change research.Satellite altimetry has been proven to be effective in detecting ice sheet variations. With the development of ICES...Elevation change monitoring of the Antarctic ice sheet has been a key issue in global change research.Satellite altimetry has been proven to be effective in detecting ice sheet variations. With the development of ICESat-2, many elevation observations can be used to derive elevation changes. However, the large amount of multitemporal data may include anomalous data points, increasing the uncertainty of the results. In this work, we improved the traditional repeat track method by introducing the Institute of Geodesy and Geophysics Ⅲ(IGGⅢ) method to obtain high-accuracy estimates of elevation change. The improved method was applied to analyze elevation changes along the transect from Zhongshan Station to Dome A in East Antarctica via ICESat-2 satellite altimetry data. The results show that the improved and traditional methods yield consistent numerical and spatial elevation change distributions. The elevation change calculated via the traditional method is 0.033 ± 0.131 m/yr, whereas the elevation change estimated via the IGGⅢ robust estimation method is 0.033 ± 0.109 m/yr from March 2019 to December 2021.In terms of spatial distribution, elevation changes in inland areas remain close to equilibrium, whereas regions with steeper ice sheet margins exhibit positive accumulation trends in elevation changes. The improved method reduces the standard error of the adjustment function from 0.975 to 0.691 m/yr. The improvement is particularly remarkable in the area between 72°S and 77°S. The results demonstrate that the IGGⅢ method effectively reduces errors caused by the inclusion of anomalous data and maintains the high data utilization rate of repeat-orbit methods.展开更多
Glaciers in the central Qilian Mountains provide important water resources for the arid Hexi corridor and Qaidam Basin;however,changes in these glaciers interact with climate change.Twenty-four bi-static image pairs o...Glaciers in the central Qilian Mountains provide important water resources for the arid Hexi corridor and Qaidam Basin;however,changes in these glaciers interact with climate change.Twenty-four bi-static image pairs of TerraSAR-X add-on for Digital Elevation Measurement(TanDEM-X)data,in addition to a Shuttle Radar Topography Mission-C/X band digital elevation model,and the technology of iterative differential synthetic aperture radar interferometry were used to carry out glacier elevation change analysis in the central Qilian Mountains in China during 2000–2014.Glacier elevation changed with an average rate of(−0.47±0.06)m yr^(−1),while changes in elevation of(−0.51±0.06)m yr^(−1) and(−0.44±0.06)m yr^(−1) were found in the northern(including the Zoulangnan,Tuolai,and Tuolainan mountains)and southern(including the Shulenan and Hark mountains)regions,respectively.Summer mean temperature has risen by 0.51℃(10 yr)^(−1)in the northern region and 0.48℃(10 yr)^(−1) in the southern region during 1989–2014;however,the change in amplitude of annual precipitation was 2.69 mm yr^(−1) in the northern region and 4.77 mm yr^(−1) in the southern region for the same period.These changes can be ascribed as major driving factors for the differences in the changes in glacial elevation in the northern and southern regions.Four types of glaciers existed in the region when considering the change in elevation of the glacial tongue and variation in the position of the glacial terminus:surging,advancing,intensively retreating,and slightly retreating glaciers.If elevation decreased more than 20 m on the part of glacier tongue,the glacier terminus position had commonly retreated more than 100 m.展开更多
Glaciers play an important role in the climate system. The elevation change of a glacier is an important parameter in studies of glacier dynamics. Only a few ground-based measurements of high mountain glaciers are ava...Glaciers play an important role in the climate system. The elevation change of a glacier is an important parameter in studies of glacier dynamics. Only a few ground-based measurements of high mountain glaciers are available due to their remoteness, high elevation, and complex topography. The acquisition from the German Tan DEM-X(Terra SAR-X add-on for Digital Elevation Measurement) SAR imaging configuration provides a reliable data sources for studying the elevation change of glaciers. In this study, the bistatic Tan DEM-X data that cover the Geladandong Mountain on the Tibetan Plateau were processed with SAR interferometry technique and the elevation changes of the mountain's glaciers during 2000–2014 were obtained. The results indicated that although distinct positive and negative elevation changes were found for different glacier tongues, the mean elevation change was about-0.14±0.26 m a-1. Geoscience Laser Altimeter System(GLAS) data were obtained for comparison and verification. The investigation using GLAS data demonstrated the efficacy of the proposed method in determining glacier elevation change. Thus, the presented approach is appropriate for monitoring glacier elevation change and it constitutes a valuable tool for studies of glacier dynamics.展开更多
The Heihe River Basin is the second largest inland river basin in the arid regions of Northwest China. Glaciers provide a large proportion of water resources for human production and living. Studies of glacier changes...The Heihe River Basin is the second largest inland river basin in the arid regions of Northwest China. Glaciers provide a large proportion of water resources for human production and living. Studies of glacier changes and their impact on water resources in the arid lands are of vital importance. A joint expedition was carried out in 2010 for investigating glaciers in the Hulugou Basin, which is located in the upper reaches of Heihe River. There- fore, glacier changes in the Hulugou Basin of central Qilian Mountains during the past 50 years were analyzed in this study by comparing topographic maps, satellite images, digital elevation models and field observation data from different periods. Results showed that the total area of the 6 glaciers in the Hulugou Basin decreased by 0.590±0.005 km^2 during the period 1956-2011, corresponding to a loss of 40.7% over the total area in 1956. The average area reduction rate of the 6 glaciers is 0.011 km^2/a. During the past five decades, the glacier shrinkage was accelerated. The changes in glacier ice surface elevation ranged from -15 to 3 m with an average thinning of 10±8 m or an annual decrease of 0.23±0.18 m （0.20±0.15 m/a water equivalent） for the period 1956-2000. The area of Shiyi Glacier in the Hulugou Basin decreased from 0.64 km^2 in 1956 to 0.53 km2 in 2011 with a reduction rate of 17.2%. The Shiyi Glacier had been divided into two separated glaciers because of severe melting. Comparative analysis showed that glacier shrinkage in the Hulugou Basin is more serious than that in the other regions of Qilian Mountains.展开更多
Subtraction of elevation datasets(e.g.digital elevation models(DEMs)and non-continuous elevation points)acquired at different times is a useful method to monitor landform surface change.Due to heavy post-processing of...Subtraction of elevation datasets(e.g.digital elevation models(DEMs)and non-continuous elevation points)acquired at different times is a useful method to monitor landform surface change.Due to heavy post-processing of these elevation datasets,multi-source errors are introduced into the resulting elevation data products.To improve the estimation of elevation change,co-registration of elevation datasets is a prerequisite.This paper presents an open-source automated GIS tool(arc Pycor)for co-registering elevation datasets.arc Pycor is coded in Python 2.7 and is run via Arc GIS for Desktop.The performances of arc Pycor have been evaluated using a series of experiments.In benchmark tests,the resolved co-registration vectors of arc Pycor are compared to the predefined shift vectors obtained by artificially misaligning the slave DEMs from the master elevation datasets.Results show that arc Pycor is able to co-register DEMs with relative high accuracy and can well align slave DEMs to non-continuous elevation points,which indicates its robustness in co-registering of elevation datasets.arc Pycor is also able to co-register multi-sourced DEMs of different resolutions in mountain areas.展开更多
Accurate measurements of glacier elevation changes play a crucial role in various glaciological studies related to glacier dynamics and mass balance. In this paper, glacier elevation changes of Urumqi Glacier No.1 bet...Accurate measurements of glacier elevation changes play a crucial role in various glaciological studies related to glacier dynamics and mass balance. In this paper, glacier elevation changes of Urumqi Glacier No.1 between August 2015 and August 2017 were investigated using Sentinel-1 A data and DInSAR technology. Meanwhile, the atmospheric delay error was corrected with the MODIS MOD05L2 products. The weight selection iteration method was applied to calibrate the glacier elevation changes in the mass balance years 2015-2016 and 2016-2017. Finally, the geodetic method was employed to calculate the elevation change values of individual stakes of Urumqi Glacier No.1. Moreover, the elevation change values corrected by the weight selection iteration method were verified. Results showed as follows:(1) the elevation of Urumqi Glacier No.1 glacier affected by atmospheric delay was 1.270 cm from 2015 to 2016. The glacier elevation affected by atmospheric delay from 2016 to 2017 was 1.071 cm.(2) The elevation change value of Urumqi Glacier No.1 was-1.101 m from 2015 to 2016, and the elevation of Urumqi Glacier No.1 decreased by 1.299 m from 2016 to 2017. The overall thickness of Urumqi Glacier No. 1 was thinning.(3) By comparing the elevation change results of individual stakes with corresponding points corrected by the weight selection iteration method, the mean squared errors of difference were 0.343 m and 0.280 m between the two mass balance years, respectively.(4) The accuracy of elevation change in non-glaciated areas was 0.039 m from 2015 to 2016 and 0.034 m from 2016 to 2017. Therefore, it is reliable to use Sentinel-1 A data and the study method proposed in this paper to calculate the elevation change of mountain glaciers with very low horizontal movement.展开更多
The expected responses of ice sheets to climate warming are growth in the thickness of the inland ice areas and thinning near the margins.In recent decades,researchers have identified glacier acceleration along Antarc...The expected responses of ice sheets to climate warming are growth in the thickness of the inland ice areas and thinning near the margins.In recent decades,researchers have identified glacier acceleration along Antarctic ice sheet coastal margins.However,the study of ice sheet interiors where seasonal accumulation eventually balances ice wastage at the lower elevation is poorly understood.In this paper,the ice sheet elevation change around Dome A region is analyzed from 2002 to 2012 using two million elevation change measurements from EnviSat satellite radar altimeter data covering an area of about 7000 km2.A declining trend of 0.572±1.31 mm/year which means that the Dome A region was in balance during the last decade can be captured.In addition,two obvious changes in accumulation which divide elevation change time series into three independent equilibration stages are also extracted.In order to explain this phenomenon,two speculations related to snowfall and firn compaction are proposed in this paper.展开更多
Impact of satellite elevation cutoff angle and position dilution of precision(PDOP)mask change on epoch-wise variance components of unmodeled effects that accompany relative Global Positioning System(GPS)positioning i...Impact of satellite elevation cutoff angle and position dilution of precision(PDOP)mask change on epoch-wise variance components of unmodeled effects that accompany relative Global Positioning System(GPS)positioning is presented herein.Data used for this study refer to the winter and summer periods of the years with minimal(2008)and maximal(2013)solar activity.These data were collected every 30 s in static mode,at two permanent GPS stations located in Montenegro,establishing a mediumdistance(116-km-long)baseline with a height difference of approximately 760 m between its endpoints.The study showed that changing satellite elevation cutoff angle,with a fixed PDOP mask,affects epochwise two-way nested ANOVA estimates of variances related to the‘far-field’multipath(considered as the nested factor herein)and the combined unmodeled effect of tropospheric and ionospheric refraction(considered as the nesting factor herein).However,changing of PDOP mask,with a fixed satellite elevation cutoff angle,doesn’t affect epoch-wise two-way nested ANOVA estimate of variance of the combined unmodeled effect of tropospheric and ionospheric refraction,but,generally,affects the estimate of variance of the‘far-field’multipath(possibly mixed with a part of a‘shorter-term’ionospheric refraction),which is especially pronounced for the summer period.It should also be noted that there is a significant influence of satellite elevation cutoff angle change on both epoch-wise horizontal and vertical position accuracy,only for the summer period,especially in the presence of maximal solar activity,while there is no significant impact of PDOP mask change on epoch-wise positional accuracy.展开更多
Rapid climate warming is leading to a notable increase in glacier recession and the formation of glacial lakes,which are becoming increasingly characteristic of high mountain regions globally.These severe cryospheric ...Rapid climate warming is leading to a notable increase in glacier recession and the formation of glacial lakes,which are becoming increasingly characteristic of high mountain regions globally.These severe cryospheric changes critically affect regional water supply,increase geohazards,and threaten lives and livelihoods.This study records regional glaciers and glacial lake dynamics for the period 1990 to 2024,considers the implications of these changes for glacial lake outburst floods(GLOFs)and assesses the potential future flood hazard.Several remotely sensed and reanalysis datasets from 1990 to 2024 are employed to investigate changes in glacier and lake areas.The results highlight a significant reduction in the Manaslu(-0.72±0.20 km^(2)/a)and adjoining glaciers,which led to an increase in the Birendra glacial lake(0.23±0.04 km^(2)/a).Additionally,surface elevation and ice movement data reveal significant thinning of glaciers in the region,averaging-1.52±0.26 m/a,often associated with avalanches near the glacier terminus and triggering GLOFs.Using an HEC-RAS(Hydrologic Engineering Center’s River Analysis System)model,a total extension of 19.3 km of flow channels was revealed,coupled with potential increases in depth,discharge,and velocity,potentially causing massive damage downstream.Regional hazard intensity assessment indicates that five bridges,31 houses,and 1.2 km^(2)of agricultural land may be flooded,with the more populated areas near Samagaun and Banjam being the most affected.Regional climate condition,including significant rising air temperature(0.02℃/a,p<0.05)and declining precipitation(-0.24 mm/a,p<0.05),during recent decades play a crucial role in glacier dynamics and exhibit a significant spatial relation with increased temperature(R^(2)=0.62,α<0.05).Understanding regional cryospheric dynamics and associated risks is therefore essential in designing adaptive mitigation strategies.展开更多
The Puruogangri Ice Field(PIF),classified as an ultra-continental glacier,is considered extremely stable.However,several glaciers in this area have recently experienced surge events with significant instability and in...The Puruogangri Ice Field(PIF),classified as an ultra-continental glacier,is considered extremely stable.However,several glaciers in this area have recently experienced surge events with significant instability and information on surge-type glaciers(STGs)in this region remains scarce.In this study,we identified six STGs and reported the observed characteristics of their surging behavior in the region by mapping glacier boundaries,surface flow velocity information,and glacier surface elevation changes using recent Landsat satellite imagery and shuttle radar topography mission(SRTM),TanDEM,and ASTER digital elevation model(AST14DEM)data.These data provide valuable insights into recent glacial processes,flow instability,and rapid glacial movement.During the active phase of the glaciers,all exhibited frontal advances and changes in surface elevation.Owing to limitations in the satellite imagery,flow velocity profiles were only available for glaciers N1(G089071E33998N),NE1(G089128E33943N),and SE3(G089278E33913N)during the active phase.However,these results effectively reflect the velocity variations in both glaciers before,during,and after the surge.Based on the characteristics of the STG,scientific expeditions,and meteorological data,we believe that the surge in PIF was largely influenced by glacier meltwater and changes in subglacial drainage systems.展开更多
Early Miocene stratigraphy,major structural systems,magmatic emplacement,volcanic eruption,vegetation change and paleo-elevation were analyzed for the Tibetan Plateau after regional geological mapping at a scale of 1...Early Miocene stratigraphy,major structural systems,magmatic emplacement,volcanic eruption,vegetation change and paleo-elevation were analyzed for the Tibetan Plateau after regional geological mapping at a scale of 1：250,000 and related researches,revealing much more information for tectonic evolution and topographic change of the high plateau caused by Indian-Asian continental collision.Lacustrine deposits of dolostone,dolomite limestone,limestone,marl,sandstone and conglomerate of weak deformation formed extensively in the central Tibetan Plateau,indicating that vast lake complexes as large as 100,000-120,000 km2 existed in the central plateau during Early Miocene.Sporopoilen assemblages contained in the lacustrine strata indicate the disappearance of most tropical-subtropical broad-leaved trees since Early Miocene and the flourishing of dark needle-leaved trees during Early Miocene.Such vegetation changes adjusted for latitude and global climate variations demonstrate that the central Tibetan Plateau rose to ca.4,000-4,500 m and the northeastern plateau uplifted to ca.3,500-4,000 m before the Early Miocene.Intensive thrust and crustal thickening occurred in the areas surrounding central Tibetan Plateau in Early Miocene,formed Gangdise Thrust System （GTS） in the southern Lhasa block,Zedong-Renbu Thrust （ZRT） in the northern Himalaya block,Main Central Thrust （MCT） and Main Boundary Thrust （MBT） in the southern Himalaya block,and regional thrust systems in the Qaidam,Qilian,West Kunlun and Songpan-Ganzi blocks.Foreland basins formed in Early Miocene along major thrust systems,e.g.the Siwalik basin along MCT,Yalung-Zangbu Basin along GTS and ZRT,southwestern Tarim depression along West Kunlun Thrust,and large foreland basins along major thrust systems in the northeastern margin of the plateau.Intensive volcanic eruptions formed in the Qiangtang,Hoh-Xil and Kunlun blocks,porphyry granites and volcanic eruptions formed in the Nainqentanglha and Gangdise Mts.,and leucogranites and granites formed in the Himalaya and Longmenshan Mts.in Early Miocene.The K2O weight percentages of Early Miocene magmatic rocks in the Gangdise and Himlayan Mts.are found to increase with distance from the MBT,indicating the genetic relationship between regional magmatism and subduction of Indian continental plate in Early Miocene.展开更多
In the Nanliu River Estuary of Guangxi, China, the naturally expanding process of a mangrove swamp（primarily consist of Aegiceras corniculatum） over past decades is studied by satellite images. From 1988 to2013, the...In the Nanliu River Estuary of Guangxi, China, the naturally expanding process of a mangrove swamp（primarily consist of Aegiceras corniculatum） over past decades is studied by satellite images. From 1988 to2013, the area of studied mangrove swamp increased significantly from 60 hm2 to 134 hm2. The expanding process is not gradual and the significant expansion only took place in some special periods. To reveal the dynamic of mangrove swamp expansion, the evolution of tidal flat elevation and the climate change in past decades are studied respectively. The hydrodynamic condition and nutrient supply are also analysed. The study results show that the climate factors of typhoon intensity and annual minimum temperature are crucial for controlling mangrove expansion. A large number of mangrove seedlings on bare tidal flats can survive only in special climate optimum periods, which are continuous years of low typhoon intensity and high annual minimum temperature. In past decades, the scarcity of climate optimum periods resulted in a non-gradual process of mangrove expanding and a time lag of 30 years between the elevation reaching the low threshold for mangrove seedling survival and the eventual emergance of the mangrove. Compared with the climate factors,the hydrodynamic condition and nutrient supply are not important factors affecting mangrove expansion. In the future, combined with global warming, the enhanced frequency and energy of landing typhoons will most likely restrain the further expansion of this mangrove swamp.展开更多
ABSTRACT A decade-long pronounced increase in temperatures in the Arctic resulted in a global warming hotspot over the Greenland ice sheet(GrIS).Associated changes in the cryosphere were the consequence and led to a d...ABSTRACT A decade-long pronounced increase in temperatures in the Arctic resulted in a global warming hotspot over the Greenland ice sheet(GrIS).Associated changes in the cryosphere were the consequence and led to a demand for monitoring glacier changes,which are one of the major parameters to analyze the responses of the GrIS to climate change.Long-term altimetry data(e.g.ICESat,CryoSat-2,and ICESat-2)can provide elevation changes over different periods,and many methods have been developed for altimetry alone to obtain elevation changes.In this work,we provided the long-term elevation change rate data of the GrIS in three different periods using ICESat data(from February 2003 to October 2009),Cryosat-2 data(from August 2010 to October 2018)and ICESat-2 data(from October 2018 to December 2020).Optimal methods were applied to the datasets collected by three different altimeters:crossover analysis for ICESat/ICESat-2 and the surface fit method for Cryosat-2.The data revealed that the elevation change rates of the GrIS were-12.19±3.81 cm/yr,-19.70±3.61 cm/yr and-23.39±3.06 cm/yr in the three different periods,corresponding to volume change rates of-210.20±25.34 km^(3)/yr,-339.11±24.01 km^(3)/yr and-363.33±20.37 km^(3)/yr,respectively.In general,the obtained results agree with the trends discovered by other studies that were also derived from satellite altimetry data.This dataset provides the basic data for research into the impact of climate change over the GrIS.The dataset is available at https://doi.org/10.57760/sciencedb.j00076.00121.展开更多
Inter-related and spatially variable climate change factors including sea level rise,increased storminess,altered precipitation regime and increasing temperature are impacting mangroves at re-gional scales.This review...Inter-related and spatially variable climate change factors including sea level rise,increased storminess,altered precipitation regime and increasing temperature are impacting mangroves at re-gional scales.This review highlights extreme regional variation in climate change threats and impacts,and how these factors impact the structure of mangrove communities,their biodiversity and geo-morphological setting.All these factors interplay to determine spatially variable resiliency to climate change impacts,and because mangroves are varied in type and geographical location,these systems are good models for understanding such interactions at different scales.Sea level rise is likely to in-fluence mangroves in all regions although local impacts are likely to be more varied.Changes in the frequency and intensity of storminess are likely to have a greater impact on N and Central America,Asia,Australia,and East Africa than West Africa and S.America.This review also highlights the nu-merous geographical knowledge gaps of climate change impacts,with some regions particularly understudied(e.g.,Africa and the Middle East).While there has been a recent drive to address these knowledge gaps especially in South America and Asia,further research is required to allow research-ers to tease apart the processes that influence both vulnerability and resilience to climate change.A more globally representative view of mangroves would allow us to better understand the importance of mangrove type and landscape setting in determining system resiliency to future climate change.展开更多
基金supported by the National Key Research and Development Program of China under grant numbers 2023YFC2809103 and 2024YFC2813505the National Natural Science Foundation of China under the grant number 41706216+2 种基金the Fundamental Research Funds for the Central Universities under grant numbers 2042022kf1204,2042022kf1069,2042023gf0012,2042022dx0001the Hubei Provincial Natural Science Foundation of China under grant number 2022CFB081the State Key Laboratory of Geodesy and Earth's Dynamics,Innovation Academy for Precision Measurement Science and Technology under grant number SKLGED2023-2-6。
文摘Ice shelves are important passageways for ice sheets flowing into the ocean.Through iceberg calving and basal melting,ice shelves exert considerable influence on the mass balance of the Antarctic Ice Sheet and glacier stability.The Ross Ice Shelf(RIS),the largest body of floating ice on Earth,plays an essential role in any changes in the mass balance of the Antarctic Ice Sheet.The long-term elevation change trend of RIS has been calculated with multiple satellite altimetry in previous studies.However,the seasonal variations were less revealed.Based on crossover analysis and indirect observation adjustments,this study proposed a new method for constructing seasonal records for surface elevation changes in the RIS using ICESat laser altimetry data from 2003 to 2009.The results showed that surface elevation changes exhibited seasonal variations with fluctuations over 20 cm,and the seasonal change characteristics were closely related to the temperature.Interannual variations in RIS surface elevation decreased from 2003 to2009 at a rate of 2 cm/yr.From March 2003 to April 2007,the surface elevation decreased at 3.7 cm/yr;however,after April 2007,the surface elevation increased at 5.5 cm/yr.The more recent stages of surface elevation growth have been influenced by reductions in the summer basal melt,which is related to the decreases in ocean heat content.
基金supported by the National Key Research and Development Program of China under grant number 2023YFC2809103the Fundamental Research Funds for the Central Universities under grant numbers 2042022kf1204, 2042022kf1069, 2042023gf0012, 2042022dx0001+1 种基金the Hubei Provincial Natural Science Foundation of China under grant number 2022CFB081the State Key Laboratory of Geodesy and Earth's Dynamics, Innovation Academy for Precision Measurement Science and Technology under grant number SKLGED2023-2-6
文摘Elevation change monitoring of the Antarctic ice sheet has been a key issue in global change research.Satellite altimetry has been proven to be effective in detecting ice sheet variations. With the development of ICESat-2, many elevation observations can be used to derive elevation changes. However, the large amount of multitemporal data may include anomalous data points, increasing the uncertainty of the results. In this work, we improved the traditional repeat track method by introducing the Institute of Geodesy and Geophysics Ⅲ(IGGⅢ) method to obtain high-accuracy estimates of elevation change. The improved method was applied to analyze elevation changes along the transect from Zhongshan Station to Dome A in East Antarctica via ICESat-2 satellite altimetry data. The results show that the improved and traditional methods yield consistent numerical and spatial elevation change distributions. The elevation change calculated via the traditional method is 0.033 ± 0.131 m/yr, whereas the elevation change estimated via the IGGⅢ robust estimation method is 0.033 ± 0.109 m/yr from March 2019 to December 2021.In terms of spatial distribution, elevation changes in inland areas remain close to equilibrium, whereas regions with steeper ice sheet margins exhibit positive accumulation trends in elevation changes. The improved method reduces the standard error of the adjustment function from 0.975 to 0.691 m/yr. The improvement is particularly remarkable in the area between 72°S and 77°S. The results demonstrate that the IGGⅢ method effectively reduces errors caused by the inclusion of anomalous data and maintains the high data utilization rate of repeat-orbit methods.
基金This work was supported by the National Nature Science Foundation of China[41671065]Key Research Program of Hunan University of Arts and Science[20ZD03]+1 种基金Applied Economics[XJT(2018)469]the Hunan Nature Science Foundation[2021JJ30474].
文摘Glaciers in the central Qilian Mountains provide important water resources for the arid Hexi corridor and Qaidam Basin;however,changes in these glaciers interact with climate change.Twenty-four bi-static image pairs of TerraSAR-X add-on for Digital Elevation Measurement(TanDEM-X)data,in addition to a Shuttle Radar Topography Mission-C/X band digital elevation model,and the technology of iterative differential synthetic aperture radar interferometry were used to carry out glacier elevation change analysis in the central Qilian Mountains in China during 2000–2014.Glacier elevation changed with an average rate of(−0.47±0.06)m yr^(−1),while changes in elevation of(−0.51±0.06)m yr^(−1) and(−0.44±0.06)m yr^(−1) were found in the northern(including the Zoulangnan,Tuolai,and Tuolainan mountains)and southern(including the Shulenan and Hark mountains)regions,respectively.Summer mean temperature has risen by 0.51℃(10 yr)^(−1)in the northern region and 0.48℃(10 yr)^(−1) in the southern region during 1989–2014;however,the change in amplitude of annual precipitation was 2.69 mm yr^(−1) in the northern region and 4.77 mm yr^(−1) in the southern region for the same period.These changes can be ascribed as major driving factors for the differences in the changes in glacial elevation in the northern and southern regions.Four types of glaciers existed in the region when considering the change in elevation of the glacial tongue and variation in the position of the glacial terminus:surging,advancing,intensively retreating,and slightly retreating glaciers.If elevation decreased more than 20 m on the part of glacier tongue,the glacier terminus position had commonly retreated more than 100 m.
基金supported by the National Science Foundation of China (41590852, 41001264)the International Science & Technology Cooperation Program of China (2010DFB23380)+1 种基金International Partnership Program of Chinese Academy of Sciences (131C11KYSB20160061)supported by the DLR AO project (GEOL0447)
文摘Glaciers play an important role in the climate system. The elevation change of a glacier is an important parameter in studies of glacier dynamics. Only a few ground-based measurements of high mountain glaciers are available due to their remoteness, high elevation, and complex topography. The acquisition from the German Tan DEM-X(Terra SAR-X add-on for Digital Elevation Measurement) SAR imaging configuration provides a reliable data sources for studying the elevation change of glaciers. In this study, the bistatic Tan DEM-X data that cover the Geladandong Mountain on the Tibetan Plateau were processed with SAR interferometry technique and the elevation changes of the mountain's glaciers during 2000–2014 were obtained. The results indicated that although distinct positive and negative elevation changes were found for different glacier tongues, the mean elevation change was about-0.14±0.26 m a-1. Geoscience Laser Altimeter System(GLAS) data were obtained for comparison and verification. The investigation using GLAS data demonstrated the efficacy of the proposed method in determining glacier elevation change. Thus, the presented approach is appropriate for monitoring glacier elevation change and it constitutes a valuable tool for studies of glacier dynamics.
基金funded by the National Basic Research Program of China (2013CBA01801)the National Natural Science Foundation of China (41301069, 41471058)+1 种基金the Funds for Creative Research Groups of China (41121001)the Special Financial Grant from the China Postdoctoral Science Foundation (2014T70948)
文摘The Heihe River Basin is the second largest inland river basin in the arid regions of Northwest China. Glaciers provide a large proportion of water resources for human production and living. Studies of glacier changes and their impact on water resources in the arid lands are of vital importance. A joint expedition was carried out in 2010 for investigating glaciers in the Hulugou Basin, which is located in the upper reaches of Heihe River. There- fore, glacier changes in the Hulugou Basin of central Qilian Mountains during the past 50 years were analyzed in this study by comparing topographic maps, satellite images, digital elevation models and field observation data from different periods. Results showed that the total area of the 6 glaciers in the Hulugou Basin decreased by 0.590±0.005 km^2 during the period 1956-2011, corresponding to a loss of 40.7% over the total area in 1956. The average area reduction rate of the 6 glaciers is 0.011 km^2/a. During the past five decades, the glacier shrinkage was accelerated. The changes in glacier ice surface elevation ranged from -15 to 3 m with an average thinning of 10±8 m or an annual decrease of 0.23±0.18 m （0.20±0.15 m/a water equivalent） for the period 1956-2000. The area of Shiyi Glacier in the Hulugou Basin decreased from 0.64 km^2 in 1956 to 0.53 km2 in 2011 with a reduction rate of 17.2%. The Shiyi Glacier had been divided into two separated glaciers because of severe melting. Comparative analysis showed that glacier shrinkage in the Hulugou Basin is more serious than that in the other regions of Qilian Mountains.
基金supported by the National Natural Science Foundation of China(grant 41901088)the China Postdoctoral Science Foundation(grant 2020M670423)+2 种基金supported by the National Natural Science Foundation of China(grant 41530748)the second Tibetan Plateau Scientific Expedition and Research Program(grant 2019QZKK0202)the 13th Five-year Informatization Plan of Chinese Academy of Sciences(grant XXH13505-06)。
文摘Subtraction of elevation datasets(e.g.digital elevation models(DEMs)and non-continuous elevation points)acquired at different times is a useful method to monitor landform surface change.Due to heavy post-processing of these elevation datasets,multi-source errors are introduced into the resulting elevation data products.To improve the estimation of elevation change,co-registration of elevation datasets is a prerequisite.This paper presents an open-source automated GIS tool(arc Pycor)for co-registering elevation datasets.arc Pycor is coded in Python 2.7 and is run via Arc GIS for Desktop.The performances of arc Pycor have been evaluated using a series of experiments.In benchmark tests,the resolved co-registration vectors of arc Pycor are compared to the predefined shift vectors obtained by artificially misaligning the slave DEMs from the master elevation datasets.Results show that arc Pycor is able to co-register DEMs with relative high accuracy and can well align slave DEMs to non-continuous elevation points,which indicates its robustness in co-registering of elevation datasets.arc Pycor is also able to co-register multi-sourced DEMs of different resolutions in mountain areas.
基金funded by the Natural Science Foundation of China (Grants No.41761134093)Gansu Provincial Department of Education: ‘Star of Innovation’ Project of Excellent Graduate Students (Grants No.2021CXZX-188)。
文摘Accurate measurements of glacier elevation changes play a crucial role in various glaciological studies related to glacier dynamics and mass balance. In this paper, glacier elevation changes of Urumqi Glacier No.1 between August 2015 and August 2017 were investigated using Sentinel-1 A data and DInSAR technology. Meanwhile, the atmospheric delay error was corrected with the MODIS MOD05L2 products. The weight selection iteration method was applied to calibrate the glacier elevation changes in the mass balance years 2015-2016 and 2016-2017. Finally, the geodetic method was employed to calculate the elevation change values of individual stakes of Urumqi Glacier No.1. Moreover, the elevation change values corrected by the weight selection iteration method were verified. Results showed as follows:(1) the elevation of Urumqi Glacier No.1 glacier affected by atmospheric delay was 1.270 cm from 2015 to 2016. The glacier elevation affected by atmospheric delay from 2016 to 2017 was 1.071 cm.(2) The elevation change value of Urumqi Glacier No.1 was-1.101 m from 2015 to 2016, and the elevation of Urumqi Glacier No.1 decreased by 1.299 m from 2016 to 2017. The overall thickness of Urumqi Glacier No. 1 was thinning.(3) By comparing the elevation change results of individual stakes with corresponding points corrected by the weight selection iteration method, the mean squared errors of difference were 0.343 m and 0.280 m between the two mass balance years, respectively.(4) The accuracy of elevation change in non-glaciated areas was 0.039 m from 2015 to 2016 and 0.034 m from 2016 to 2017. Therefore, it is reliable to use Sentinel-1 A data and the study method proposed in this paper to calculate the elevation change of mountain glaciers with very low horizontal movement.
基金This work was supported by the Chinese Polar Environment Comprehensive Investigation and Assessment Programmes[grant number CHINARE2015–02-04]the Public Science and Technology Research Fund Project of Surveying,Mapping and Geoinformation[grant number 201412009]+2 种基金the National Nature Science Foundation of China[grant number 41376187]the Polar Strategic Foundation[grant number 20120107]the Advance Research Program of Civil Aerospace Technology[grant number D040103].
文摘The expected responses of ice sheets to climate warming are growth in the thickness of the inland ice areas and thinning near the margins.In recent decades,researchers have identified glacier acceleration along Antarctic ice sheet coastal margins.However,the study of ice sheet interiors where seasonal accumulation eventually balances ice wastage at the lower elevation is poorly understood.In this paper,the ice sheet elevation change around Dome A region is analyzed from 2002 to 2012 using two million elevation change measurements from EnviSat satellite radar altimeter data covering an area of about 7000 km2.A declining trend of 0.572±1.31 mm/year which means that the Dome A region was in balance during the last decade can be captured.In addition,two obvious changes in accumulation which divide elevation change time series into three independent equilibration stages are also extracted.In order to explain this phenomenon,two speculations related to snowfall and firn compaction are proposed in this paper.
文摘Impact of satellite elevation cutoff angle and position dilution of precision(PDOP)mask change on epoch-wise variance components of unmodeled effects that accompany relative Global Positioning System(GPS)positioning is presented herein.Data used for this study refer to the winter and summer periods of the years with minimal(2008)and maximal(2013)solar activity.These data were collected every 30 s in static mode,at two permanent GPS stations located in Montenegro,establishing a mediumdistance(116-km-long)baseline with a height difference of approximately 760 m between its endpoints.The study showed that changing satellite elevation cutoff angle,with a fixed PDOP mask,affects epochwise two-way nested ANOVA estimates of variances related to the‘far-field’multipath(considered as the nested factor herein)and the combined unmodeled effect of tropospheric and ionospheric refraction(considered as the nesting factor herein).However,changing of PDOP mask,with a fixed satellite elevation cutoff angle,doesn’t affect epoch-wise two-way nested ANOVA estimate of variance of the combined unmodeled effect of tropospheric and ionospheric refraction,but,generally,affects the estimate of variance of the‘far-field’multipath(possibly mixed with a part of a‘shorter-term’ionospheric refraction),which is especially pronounced for the summer period.It should also be noted that there is a significant influence of satellite elevation cutoff angle change on both epoch-wise horizontal and vertical position accuracy,only for the summer period,especially in the presence of maximal solar activity,while there is no significant impact of PDOP mask change on epoch-wise positional accuracy.
基金supported by the Gansu Provincial Science and Technology Program(22ZD6FA005)the Gansu Postdoctoral Science Foundation(E339880202).
文摘Rapid climate warming is leading to a notable increase in glacier recession and the formation of glacial lakes,which are becoming increasingly characteristic of high mountain regions globally.These severe cryospheric changes critically affect regional water supply,increase geohazards,and threaten lives and livelihoods.This study records regional glaciers and glacial lake dynamics for the period 1990 to 2024,considers the implications of these changes for glacial lake outburst floods(GLOFs)and assesses the potential future flood hazard.Several remotely sensed and reanalysis datasets from 1990 to 2024 are employed to investigate changes in glacier and lake areas.The results highlight a significant reduction in the Manaslu(-0.72±0.20 km^(2)/a)and adjoining glaciers,which led to an increase in the Birendra glacial lake(0.23±0.04 km^(2)/a).Additionally,surface elevation and ice movement data reveal significant thinning of glaciers in the region,averaging-1.52±0.26 m/a,often associated with avalanches near the glacier terminus and triggering GLOFs.Using an HEC-RAS(Hydrologic Engineering Center’s River Analysis System)model,a total extension of 19.3 km of flow channels was revealed,coupled with potential increases in depth,discharge,and velocity,potentially causing massive damage downstream.Regional hazard intensity assessment indicates that five bridges,31 houses,and 1.2 km^(2)of agricultural land may be flooded,with the more populated areas near Samagaun and Banjam being the most affected.Regional climate condition,including significant rising air temperature(0.02℃/a,p<0.05)and declining precipitation(-0.24 mm/a,p<0.05),during recent decades play a crucial role in glacier dynamics and exhibit a significant spatial relation with increased temperature(R^(2)=0.62,α<0.05).Understanding regional cryospheric dynamics and associated risks is therefore essential in designing adaptive mitigation strategies.
基金The Second Tibetan Plateau Scientific Expedition and Research Program,No.2019QZKK020102National Natural Science Foundation of China,No.42130516。
文摘The Puruogangri Ice Field(PIF),classified as an ultra-continental glacier,is considered extremely stable.However,several glaciers in this area have recently experienced surge events with significant instability and information on surge-type glaciers(STGs)in this region remains scarce.In this study,we identified six STGs and reported the observed characteristics of their surging behavior in the region by mapping glacier boundaries,surface flow velocity information,and glacier surface elevation changes using recent Landsat satellite imagery and shuttle radar topography mission(SRTM),TanDEM,and ASTER digital elevation model(AST14DEM)data.These data provide valuable insights into recent glacial processes,flow instability,and rapid glacial movement.During the active phase of the glaciers,all exhibited frontal advances and changes in surface elevation.Owing to limitations in the satellite imagery,flow velocity profiles were only available for glaciers N1(G089071E33998N),NE1(G089128E33943N),and SE3(G089278E33913N)during the active phase.However,these results effectively reflect the velocity variations in both glaciers before,during,and after the surge.Based on the characteristics of the STG,scientific expeditions,and meteorological data,we believe that the surge in PIF was largely influenced by glacier meltwater and changes in subglacial drainage systems.
基金supported by the China Geological Survey under grants Nos.1212011120185 and 1212011221111the Ministry of Science and Technology of China under grant 2006DFB21330
文摘Early Miocene stratigraphy,major structural systems,magmatic emplacement,volcanic eruption,vegetation change and paleo-elevation were analyzed for the Tibetan Plateau after regional geological mapping at a scale of 1：250,000 and related researches,revealing much more information for tectonic evolution and topographic change of the high plateau caused by Indian-Asian continental collision.Lacustrine deposits of dolostone,dolomite limestone,limestone,marl,sandstone and conglomerate of weak deformation formed extensively in the central Tibetan Plateau,indicating that vast lake complexes as large as 100,000-120,000 km2 existed in the central plateau during Early Miocene.Sporopoilen assemblages contained in the lacustrine strata indicate the disappearance of most tropical-subtropical broad-leaved trees since Early Miocene and the flourishing of dark needle-leaved trees during Early Miocene.Such vegetation changes adjusted for latitude and global climate variations demonstrate that the central Tibetan Plateau rose to ca.4,000-4,500 m and the northeastern plateau uplifted to ca.3,500-4,000 m before the Early Miocene.Intensive thrust and crustal thickening occurred in the areas surrounding central Tibetan Plateau in Early Miocene,formed Gangdise Thrust System （GTS） in the southern Lhasa block,Zedong-Renbu Thrust （ZRT） in the northern Himalaya block,Main Central Thrust （MCT） and Main Boundary Thrust （MBT） in the southern Himalaya block,and regional thrust systems in the Qaidam,Qilian,West Kunlun and Songpan-Ganzi blocks.Foreland basins formed in Early Miocene along major thrust systems,e.g.the Siwalik basin along MCT,Yalung-Zangbu Basin along GTS and ZRT,southwestern Tarim depression along West Kunlun Thrust,and large foreland basins along major thrust systems in the northeastern margin of the plateau.Intensive volcanic eruptions formed in the Qiangtang,Hoh-Xil and Kunlun blocks,porphyry granites and volcanic eruptions formed in the Nainqentanglha and Gangdise Mts.,and leucogranites and granites formed in the Himalaya and Longmenshan Mts.in Early Miocene.The K2O weight percentages of Early Miocene magmatic rocks in the Gangdise and Himlayan Mts.are found to increase with distance from the MBT,indicating the genetic relationship between regional magmatism and subduction of Indian continental plate in Early Miocene.
基金The National Natural Science Foundation of China under contract No.41306075the Natural Science Foundation of Guangxi Province under contract No.2014GXNSFBA118222the Foundation of Guangxi Academy of Sciences under contract No.12YJ25HS16
文摘In the Nanliu River Estuary of Guangxi, China, the naturally expanding process of a mangrove swamp（primarily consist of Aegiceras corniculatum） over past decades is studied by satellite images. From 1988 to2013, the area of studied mangrove swamp increased significantly from 60 hm2 to 134 hm2. The expanding process is not gradual and the significant expansion only took place in some special periods. To reveal the dynamic of mangrove swamp expansion, the evolution of tidal flat elevation and the climate change in past decades are studied respectively. The hydrodynamic condition and nutrient supply are also analysed. The study results show that the climate factors of typhoon intensity and annual minimum temperature are crucial for controlling mangrove expansion. A large number of mangrove seedlings on bare tidal flats can survive only in special climate optimum periods, which are continuous years of low typhoon intensity and high annual minimum temperature. In past decades, the scarcity of climate optimum periods resulted in a non-gradual process of mangrove expanding and a time lag of 30 years between the elevation reaching the low threshold for mangrove seedling survival and the eventual emergance of the mangrove. Compared with the climate factors,the hydrodynamic condition and nutrient supply are not important factors affecting mangrove expansion. In the future, combined with global warming, the enhanced frequency and energy of landing typhoons will most likely restrain the further expansion of this mangrove swamp.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA19070202)the Joint Project of the Chinese Academy of Science(CAS)entitled Using Earth Observations to Address Ecology and Environment Change in the Pan-Antarctic Cryosphere(No.183611KYSB20200059)the Open Research Program of the International Research Center of Big Data for Sustainable Development Goals(No.CBAS2022ORP04).
文摘ABSTRACT A decade-long pronounced increase in temperatures in the Arctic resulted in a global warming hotspot over the Greenland ice sheet(GrIS).Associated changes in the cryosphere were the consequence and led to a demand for monitoring glacier changes,which are one of the major parameters to analyze the responses of the GrIS to climate change.Long-term altimetry data(e.g.ICESat,CryoSat-2,and ICESat-2)can provide elevation changes over different periods,and many methods have been developed for altimetry alone to obtain elevation changes.In this work,we provided the long-term elevation change rate data of the GrIS in three different periods using ICESat data(from February 2003 to October 2009),Cryosat-2 data(from August 2010 to October 2018)and ICESat-2 data(from October 2018 to December 2020).Optimal methods were applied to the datasets collected by three different altimeters:crossover analysis for ICESat/ICESat-2 and the surface fit method for Cryosat-2.The data revealed that the elevation change rates of the GrIS were-12.19±3.81 cm/yr,-19.70±3.61 cm/yr and-23.39±3.06 cm/yr in the three different periods,corresponding to volume change rates of-210.20±25.34 km^(3)/yr,-339.11±24.01 km^(3)/yr and-363.33±20.37 km^(3)/yr,respectively.In general,the obtained results agree with the trends discovered by other studies that were also derived from satellite altimetry data.This dataset provides the basic data for research into the impact of climate change over the GrIS.The dataset is available at https://doi.org/10.57760/sciencedb.j00076.00121.
基金RDW acknowledges the Rising Stars Initiative(University of Brighton),the Federal University of Para,Federal University of Parana,Federal University of Ceara,and the Federal University of São Paulo for funding and logistical support in sea level rise vul-nerability analysis in South America.DAF acknowl-edges the Asia Pacific Network for Global Change Research(ARCP2014-14NMY(B&ES))the National University of Singapore(R-109-000-141-133/R-109-000-184-720/R-109-000-158-646)who have funded sea level rise vulnerability monitoring for several sites in South east Asia.RHD is supported by the U.S.Geological Survey’s Ecosystems Mission Area.RAM acknowledges the USDA Forest Service Pacific South West Research Station and the U.S.Agency for International Development,who have funded sea level rise vulner-ability monitoring for several sites in South east Asia and the western Pacific.
文摘Inter-related and spatially variable climate change factors including sea level rise,increased storminess,altered precipitation regime and increasing temperature are impacting mangroves at re-gional scales.This review highlights extreme regional variation in climate change threats and impacts,and how these factors impact the structure of mangrove communities,their biodiversity and geo-morphological setting.All these factors interplay to determine spatially variable resiliency to climate change impacts,and because mangroves are varied in type and geographical location,these systems are good models for understanding such interactions at different scales.Sea level rise is likely to in-fluence mangroves in all regions although local impacts are likely to be more varied.Changes in the frequency and intensity of storminess are likely to have a greater impact on N and Central America,Asia,Australia,and East Africa than West Africa and S.America.This review also highlights the nu-merous geographical knowledge gaps of climate change impacts,with some regions particularly understudied(e.g.,Africa and the Middle East).While there has been a recent drive to address these knowledge gaps especially in South America and Asia,further research is required to allow research-ers to tease apart the processes that influence both vulnerability and resilience to climate change.A more globally representative view of mangroves would allow us to better understand the importance of mangrove type and landscape setting in determining system resiliency to future climate change.
