中天山南依内里切克冰川轴部二维流速及运动机制

冰川运动一定程度上会引发泥石流、滑坡等地质灾害,因此掌握冰川运动过程至关重要。冰川流速揭示冰川运动过程,而已有冰川流速构建方法未考虑冰川流动方向,揭示的冰川运动机制不够精准。选取中天山南依内里切克冰川为对象,基于2018—2020年Sentinel-1A升轨数据,利用像素偏移追踪（Pixel Offset Tracking,POT）技术获得南依内里切克冰川方位向与距离向位移场,引入冰川流动方向构建冰川主流线轴部二维流速,分析冰川运动机制。结果表明：稳定区像元偏移速度远小于冰川主流线轴部二维流速,利用POT技术构建的轴部二维流速模型监测冰川运动过程良好。2018、2019和2020年中天山南依内里切克冰川轴部二维平均流速分别为62.28 cm/d、49.41 cm/d、61.89 cm/d,消融区（冰舌）轴部二维流速随高程的降低呈先缓慢减小后逐渐增大再迅速减小趋势,冰川流速由轴部向两侧边缘递减。随着气温升高,冰川运动速度逐渐增大,气温升高可能是中天山南依内里切克冰川流速加快的主要原因。     

中天山穆什科托夫冰川跃动特征及控制机理分析

天山地区孕育着大量的跃动型冰川,目前该地区冰川跃动过程及跃动控制机制尚不明确。利用Landsat、Sentinel-1A、TerraSAR-X/TanDEM-X等多源遥感数据获得了中天山穆什科托夫冰川跃动前后的表面特征、流速和高程变化。结果表明：(1)该冰川主干表面流速从2017年夏末开始增加,在冬季流速达到最大峰值,约为4.4 m d^-1,2018年夏末急剧减小;(2)2000—2012年冰川积蓄区平均增厚9.23±4.62 m,跃动前锋形成,而冰舌部分是以减薄为主;2012—2014年冰舌部分持续减薄,中上游仍以积累为主,增厚约1.23±0.91 m;2014—2018年冰川积蓄区出现明显减薄,最大减薄42.6±1.82 m,接收区高程显著增加,最高隆起75.6±1.82 m。根据冰川表面流速及高程变化特征,确认2017—2018年为该冰川跃动活跃期;结合冰川流动定律,认为穆什科托夫冰川跃动主要受冰下水文控制。根据现有的资料及数据,推断该冰川跃动间隔约为60 a。     

基于SAR数据的山地冰川表面运动速度分析

合成孔径雷达(SAR)因其可全天时、全天候工作且不受云、雨的影响而成为遥感应用的前沿领域。SAR干涉测量(Inteferometry)利用SAR数据的相位信息可获得大地表面厘米级的形变而成为冰川表面流速监测广泛使用的手段;SAR图像相关方法(SRFT)能克服干涉测量方法因失相干严重而难以产生清晰的干涉条纹以及可见光图像质量由于云遮、雪盖限制的不足而成为目前山地冰川表面流速遥感监测的首选方式。为深入探讨SAR图像相关方法的适用性,以天山科契卡尔巴西冰川为研究区域,分析使用不同时间基线的ALOS PALSAR数据与ENVISat ASAR C-band 的图像相关方法估计冰川的表面流速,并使用实地测杆的DGPS(Differential GPS)测量流速进行对比验证,发现在冰川表碛覆盖区域使用图像相关方法测量的值与实测值有很好的一致性,而在裸露冰区域或坡度较大区域,误差比较大。比较长时间基线的SAR数据对特征识别的结果发现：时间基线为1 a的冬季获取的数据对估计值与实测值在表碛覆盖区域比较一致,这可能是由于前后两次获取图像时天气或地面状况比较接近。比较ALOS PALSAR 数据与ENVISat ASAR数据发现：波长较长的L-band(23.5 cm) 比C-band (5.7 cm)SAR数据更适合山地冰川的表面流速估计;另外在运用SAR数据特征匹配方法时也可能是极化方式的差异使得ALOS PALSAR (HH极化)数据比ENVISat ASAR(VV极化)数据更适合冰川研究。     

基于ALOSPALSAR的喜马拉雅山冰川流速分布及变化

基于2007年12月至2010年2月的12景ALOS PALSAR数据,结合SRTM,应用特征跟踪方法对喜马拉雅山冰川3个时段的流速进行了估算。结果表明,2007年冬季、2009年夏季和2009年冬季冰川流速均在0～300m·a-1之间,冰川积累区仅在夏季有较明显的运动,而冰舌部分的运动在任何季节都较为明显,并且长冰舌冰川流速沿主流线向下缓慢减小,而短冰舌冰川沿主流线向下流速不断波动变化,甚至增加。4个坡向中,东坡冰川流速最大,东南坡和西南坡次之,北坡冰川流速最小,除了与气候因素相关外,还与地形因素密切相关,从4个坡向的坡度大小来看,北坡坡度最小,也是造成北坡冰川流速最小的主要原因之一。冰川存在年际变化,即冰川冬季平均流速有所增加,增加的冰川流速在-5～18m·(2a)-1之间,并且面积大的冰川流速变化较小,面积小的冰川流速变化较大。同时冰川流速也存在季节性变化,夏季流速整体比冬季流速要大,冰川主流线上流速在夏季时波动较强烈,并且会出现多个峰值,而冬季主流线流速则较为平缓,但主流线上平均流速季节性差异并不明显。4条典型冰川流速年际变化、季节变化与研究区冰川总体特征相似,并且流速与气候特征和冰川形状之间都有密切的关系。冰川前进与退缩特征不明显,研究区冰川总体上处于平衡状态。     

中巴公路沿线冰川运动特征

中巴公路作为一条国际公路,对中国以及巴基斯坦等南亚、西亚国家有着非常重要的意义。公路穿越了帕米尔高原和喀喇昆仑山脉这个山岳冰川分布十分密集的地区,沿线的冰川前进时常威胁着公路的安全运营。利用2016年1月至2017年6月间的81景Sentinel-1合成孔径雷达影像,采用特征匹配的方法获得了1 a多来中巴公路沿线冰川的运动速度,并对比1993年和2006年的流速,对冰川前进的可能性进行分析。中巴公路沿线冰川以新疆塔吉克自治县和巴基斯坦北部城市库达巴德为界可分为北中南3部分,研究发现:北部地区冰川表面流速较为稳定,对公路安全运营的威胁很小;中部地区冰川规模普遍较小,且距离公路较远;而南部地区的大规模冰川流速较快,部分冰川积累区表面流速高达2 md~(-1)以上。为此,在南部地区选取了距离公路较近的巴托拉等4条冰川进行详细分析,结果显示帕苏冰川为1条快速运动冰川,存在冰川末端前进的可能性,巴托拉冰川、固尔金冰川和吉尔密特冰川冰舌上部流速较快,具有较强的活动特性。     

基于地基雷达点云数据的冰川表面DEM建模

冰川监测是气候变化研究的重要组成部分，为了从三维立体角度研究冰川的运动变化情况，以梅里雪山西坡的共森隆巴冰川为研究对象，基于地基雷达点云数据分别利用了不规则三角网（Triangulated Irregular Network, TIN）和反距离加权（Inverse Distance Weight, IDW）两种插值算法进行了DEM建模，以交叉验证方法分析了两种算法的关键参数对冰川DEM建模结果的影响。结果表明：(1)格网分辨率对TIN插值结果影响较大。格网分辨率较低时，会造成DEM较多的空洞，格网分辨率较高时，会导致DEM表面平滑。当格网分辨率大小选择0.75 m时，冰川表面DEM建模结果精度最高，此时R2为0.997 0,RMSE为0.457 1 m。(2)插值半径对冰川表面DEM建模效果有较大影响，插值半径较小时，空洞部分较多且较大，随着插值半径的增大，空洞部分不断减少。而格网分辨率是影响IDW插值算法精度的较大因素。虽然不同格网大小和不同插值半径下冰川DEM建模的R2和RMSE精度较高，但是DEM建模效果不理想，存在较多空洞部分，难以利用IDW算法实现完整的冰川表面建模。(3)通...     

1972～2010年西藏卡若拉冰川面积变化遥感研究

以Landsat陆地资源卫星和中国科学院寒区旱区环境与工程研究所80年代冰川矢量编目数据为数据源,利用GIS空间分析方法,提取并分析了1972~2010年西藏卡若拉冰川面积变化特征。结果表明,近38a来卡若拉冰川有不同程度的退缩,1972~1978年和1999~2010年这两个时间段变化过程较明显,退缩速率较大,尤其以冰川末端和东南坡面积变化最明显。结合冰川最近的浪卡子气象站气候要素分析,得出区域气温和降水都有升高趋势,但是气温的升高特别是冷季气温上升导致的冰雪消融超过了降水量增加的补给,是西藏卡若拉冰川退缩的主要原因。     

基于CryoSat-2雷达高度计青藏高原地区冰川高度变化提取方法对比

基于2010~2016年CryoSat-2雷达高度计SARIn模式的Level 2测高数据，结合青藏高原地区冰川矢量数据以及全球GEDM数据，通过重叠脚印法、伪平面拟合法以及较新的曲面拟合法提取青藏高原地区典型冰川冰帽的高度变化值。结果表明：①CryoSat-2测高数据应用该3种方法提取山地冰川高度变化具备可行性;②提取高度变化的3种方法各有优劣，以此提供了提取山地冰川高度变化的方法选择的依据;③应用上述3种方法获取的青藏高原地区典型冰川冰帽2010~2016年的定量高度变化结果，绝大多数的冰川都处于消融状态且3种方法提取的高度变化结果增、减趋势一致。处于西昆仑山脉的中峰冰川、古里雅、土则岗目冰川缩减速率较慢，而帕米尔高原的慕士塔格冰川缩减略快，两者的缩减速度都趋于平缓。处于念青唐古拉山脉的来古、恰青冰川高度变化速率最大。     

基于深度学习的中国第二次冰川编目半自动化更新

中国第二次冰川编目的部分数据用第一次冰川编目替代，这些数据集中分布在藏东南地区。该地区地形陡峭、气候恶劣，常年多云层覆盖，无法获取有效的光学影像，缺乏系统性的冰川调查。针对传统阈值分割方法受噪声影响大、标准Unet计算量大导致运行缓慢等问题，对Unet模型进行压缩，通过修改样本尺寸、卷积核数量和优化器等模型参数，提升模型训练效率以及冰川提取精度。利用冰川的极化特性和地形特征，选用45景ENVISAT ASAR影像和NASA DEM，基于Unet及其压缩网络进行深度学习，参考光学影像和其它辅助数据对误分和漏分的冰川逐个进行人工目视判读，完成了未更新编目的冰川边界提取及修正，并对属性进行了更新。结果表明：基于SAR影像和地形特征的深度学习可以有效识别云层覆盖区域的冰川。在第二次冰川编目未完成的地区，共有冰川8 374条，总面积5 622.65±303.58 km2，误差占总冰川面积的5.4%，整体呈退缩状态，冰川碎片化现象居多。该数据集更新了中国第二次冰川编目中的替代数据，可为探讨藏东南冰川变化和物质平衡等相关研究提供可靠的数据支撑。     

高分辨率SAR影像提取冰川面积与冰面河

冰川面积变化是冰川积累与消融的直接体现，与气候变化密切相关。遥感的方法可以为冰川的轮廓及面积监测提供可靠手段，但常用的光学遥感容易受到冰川区多变气象条件的影响。合成孔径雷达（SAR）不受天气影响，尤其是高分辨率SAR影像能够提供冰川表面丰富的细节特征，更好地监测冰川变化。应用相位一致性方法和快速行进法相结合的方法提取冰川轮廓和表面纹理。依据提取的冰川轮廓计算的冰川面积误差在5%以下，表明该方法能够准确地提取冰川面积。同时，在高分辨率SAR图像上，利用提取的冰川表面纹理信息可以有效监测到光学图像上难以识别的冰面河，而冰面河与冰川中长期消融密切相关，提取的冰面河信息将为冰川监测提供一种新的视角。     

Perito Moreno Glacier (Argentina) flow estimation by COSMO SkyMed sequence of high-resolution SAR-X imagery

The Perito Moreno Glacier (Los Glaciares National Park, Patagonia, Argentina) ice stream has been investigated using X-band SAR amplitude images collected from February to December 2009 (excluding June) at time intervals of 8 and 16 days by the COSMO SkyMed satellites. The high spatial resolution dataset (10 × 10 km swath, 1 m per pixel) reveals many details of the glacier surface and the ice velocity fields extracted from sequential image pairs by the maximum cross-correlation method cover most of the glacier area. The efficiency of the cross-correlation method improves with high spatial resolution imagery and the co-registration error of the image pair also reduces. The glacier motion detected in the period shows variability on the time scale considered, evidencing the areas of higher dynamics under different speed regimes.     

Movement estimate of the Dongkemadi Glacier on the Qinghai–Tibetan Plateau using L-band and C-band spaceborne SAR data

We measured the complex motion of the Dongkemadi Glacier on Tanggula Mountain, Qinghai–Tibetan Plateau, using two-pass differential synthetic aperture radar interferometry (InSAR) with satellite L-band and C-band SAR data. We derived detailed motion patterns of the Dongkemadi Glacier for the winter seasons of 1996, 2007 and 2008 using a European Remote sensing Satellite-1/2 (ERS-1/2) tandem InSAR pair acquired from descending orbit and a 46-day-separation Advanced Land Observing Satellite (ALOS) InSAR pair acquired from ascending orbit. In this article, we focus on an analysis of the glacier's surface motion features and a validation of the results from the InSAR using Global Positioning System (GPS) survey data. The experimental results show that the glacier flow distribution displays strong spatial variations depending on elevation. The glacier is divided into four clearly defined fast-flowing units in terms of spatial variability of the glacier speed, with evidence from both ERS and ALOS/PALSAR InSAR pairs (palsar – Phased Array type L-band Synthetic Aperture Radar). Among the four fast-flowing units, three are on the Dadongkemadi Glacier (DDG) and one on the Xiaodongkemadi Glacier (XDG). The flow patterns are generally characterized by terrain complexity for both glacier branches. The upper central area of the DDG shows slow movement, maybe due to the convergent and uptaking effect of ice from steep slope areas with opposite flow directions.     

Characteristic of Glaciers’ Movement Along Karakoram Highway

As an international highway，the Karakoram Highway(KKH) is of great importance to China，Pakistan，South-Asian and West-Asian Countries.It crosses the Karakoram Mountains，one of the most glaciers concentrated regions，and is being threatened from glaciers along KKH all the time.Currently，Synthetic Aperture Radar(SAR) have been proved reliably profitable on analyst glaciers’ movement.In this study，we analyzed the characteristics of glaciers’ movement along KKH by using feature-tracking method based on 81 scenes of Sentinel-1A data obtained between Jan.2016 to Jun.2017.And ERS-1 data in 1993 and ALOS PALSAR data in 2006 are taken as comparison for analyzing the trend of glacial surface flow rate.Our results indicated that the glacier flow streamline is basically consistent with the geometric center line of the ice tongue and the velocities increase away from both margins；summer motion was higher than winter motion.The glaciers along the KKH can be divided into three parts：north，central and south，based the boundaries of Tajik Autonomous County in Sinkiang and Khuda Abad，the northern city of Pakistan.The glacier surface velocities of the trunk is lower than 0.15md^-1and relatively stable in the northern.The scale of glaciers in the central region is generally small and far from the KKH.The glaciers in north and central regions may not affect the operation of highways.While parts of the large scale glaciers in the south region had higher velocities，particularly along the section of the highway near Batura Sar.Here，4 glaciers were selected to analyze in detail which are closest to the KKH include Batura，Pasu，Ghulkin and Gulmit in the south region.Seen from all results，the Pasu glacier has rapid motion during the study period，the normal velocity of its trunk is between 1 and 1.5 md^-1，and can reach 3 md^-1 in special place.All these 4 glaciers were flowing faster than other glaciers which reflect the high quantitative mass balance.Accordingly，the safety operation and residents’ life along the Batura Sar may be threatened by these four glaciers advance.     

基于CryoSat-2雷达高度计青藏高原地区冰川高度变化提取方法对比

基于2010~2016年CryoSat-2雷达高度计SARIn模式的Level 2测高数据,结合青藏高原地区冰川矢量数据以及全球GEDM数据,通过重叠脚印法、伪平面拟合法以及较新的曲面拟合法提取青藏高原地区典型冰川冰帽的高度变化值。结果表明：①CryoSat-2测高数据应用该3种方法提取山地冰川高度变化具备可行性;②提取高度变化的3种方法各有优劣,以此提供了提取山地冰川高度变化的方法选择的依据;③应用上述3种方法获取的青藏高原地区典型冰川冰帽2010~2016年的定量高度变化结果,绝大多数的冰川都处于消融状态且3种方法提取的高度变化结果增、减趋势一致。处于西昆仑山脉的中峰冰川、古里雅、土则岗目冰川缩减速率较慢,而帕米尔高原的慕士塔格冰川缩减略快,两者的缩减速度都趋于平缓。处于念青唐古拉山脉的来古、恰青冰川高度变化速率最大。     

Consideration of the errors inherent in mapping historical glacier positions in Austria from the ground and space (1893-2001)

The historical record of in situ measurements of the terminus positions of the Pasterze and Kleines Fleißkees glaciers in the eastern Alps of Austria is used to assess uncertainties in the measurement of decadal scale changes using satellite data. Topographic maps beginning in 1893, and satellite data from 1976 to 2001, were studied in concert with ground measurements to measure glacier changes. Ground measurements show that the tongue of the Pasterze Glacier receded ∼1150 m from 1893 to 2001, while satellite-derived measurements, using August 2001 Landsat Enhanced Thematic Mapper Plus (ETM+) data registered to an 1893 topographic map, show a recession of 1300-1800 m, with an unknown error. The measurement accuracy depends on the registration technique and the pixel resolution of the sensor when two satellite images are used. When using topographic maps, an additional source of error is the accuracy of the glacier position shown on the map. Between 1976 and 2001, Landsat-derived measurements show a recession of the terminus of the Pasterze Glacier of 479±136 m (at an average rate of 19.1 m a⁻¹) while measurements from the ground showed a recession of 428 m (at an average rate of 17.1 m a⁻¹). Four-meter resolution Ikonos satellite images from 2000 and 2001 reveal a shrinkage of 22,096±46 m² in the Pasterze tongue. The nearby Kleines Fleißkees glacier lost 30% of its area between 1984 and 2001, and the area of exposed ice increased by 0.44±0.0023 km², according to Landsat satellite measurements. As more recent satellite images are utilized, especially data that are geocoded, the uncertainty associated with measuring glacier changes has decreased. It is not possible to assess the uncertainty when an old topographic map and a satellite image are coregistered.     

Subglacial controls on dynamic thinning at Trinity-Wykeham Glacier,Prince of Wales Ice Field,Canadian Arctic

ABSTRACT

Mass loss from glaciers and ice caps represents the largest terrestrial component of current sea level rise. However, our understanding of how the processes governing mass loss will respond to climate warming remains incomplete. This study explores the relationship between surface elevation changes (dh/dt), glacier velocity changes (du/dt), and bedrock topography at the Trinity-Wykeham Glacier system (TWG), Canadian High Arctic, using a range of satellite and airborne datasets. We use measurements of dh/dt from ICESat (2003–2009) and CryoSat-2 (2010–2016) repeat observations to show that rates of surface lowering increased from 4 m yr^?1 to 6 m yr^?1 across the lowermost 10 km of the TWG. We show that surface flow rates at both Trinity Glacier and Wykeham Glacier doubled over 16 years, during which time the ice front retreated 4.45 km. The combination of thinning, acceleration and retreat of the TWG suggests that a dynamic thinning mechanism is responsible for the observed changes, and we suggest that both glaciers have transitioned from fully grounded to partially floating. Furthermore, by comparing the separate glacier troughs we suggest that the dynamic changes are modulated by both lateral friction from the valley sides and the complex geometry of the bed. Further, the presence of bedrock ridges induces crevassing on the surface and provides a direct link for surface meltwater to reach the bed. We observe supraglacial lakes that drain at the end of summer and are concurrent with a reduction in glacier velocity, suggesting hydrological connections between the surface and the bed significantly impact ice flow. The bedrock topography thus has a primary influence on the nature of the changes in ice dynamics observed over the last decade.     

Modelling glacier topography in Antarctica using unmanned aerial survey: assessment of opportunities

We discuss the application of unmanned aerial systems (UASs) and UAS-derived data to model glacier topography for detecting and analysing slow and rapid changes in glacier surfaces. The study was conducted in East Antarctica in the austral summer 2016/2017. The surveyed areas included an eastern part of the Larsemann Hills, an Airfield of the Progress Station, an initial section of a Sledge route from the Progress to Vostok Stations, and a north-western margin of the Dålk Glacier. We used a Geoscan 201 Geodesy, a professional-grade flying-wing UAS. For the photogrammetric processing, we utilized the Agisoft PhotoScan software. The direct georeferencing approach was applied. Several high-resolution, multitemporal digital elevation models (DEMs) for surveyed areas were produced. The DEM accuracy was estimated in the absence of ground control points and reference DEMs. We determined the ice flow velocity within the Airfield area and the Sledge route zone, where marked points were installed and moved together with the ice surface. We found that UAS imagery can be used for real-time monitoring of open and some snow-covered crevasses of various sizes. Wind-driven snow microforms are also well recognizable on UAS-derived aerial images. The 2017 Dålk Glacier catastrophic subsidence demonstrated that monitoring and studying such events in glaciers and ice sheets are almost impossible without UASs. Optimal meteorological conditions were empirically determined for conducting unmanned aerial survey to obtain images suitable for subsequent photogrammetric processing and DEM generation. Finally, we discuss adaptation of equipment and software to the Antarctic environment.     

Glacier changes in Glacier Bay,Alaska, during 2000–2012

This article presents measurements of glacier surface areas, mean snow line altitude (MSLA) values, mean snow accumulation area ratio (MAAR) values, and elevation changes in the Glacier Bay, Alaska, using Landsat Thematic Mapper (TM)/Landsat Enhanced Thematic Mapper Plus (ETM+) images and digital elevation models (DEMs) from Shuttle Radar Topography Mission (SRTM) and interferometric synthetic aperture radar (IFSAR) data during 2000–2012. Glacier area estimation results showed that Desolation glacier and Fairweather glacier have lost 2.6% and 2.2% of the glacier area, respectively. Only minor surface area changes were seen in Cascade glacier, Crillon glacier, and Lituya glacier during the study period. The results of MSLA and MAAR showed that the MSLA of Fairweather glacier, Lituya glacier, and Desolation glacier increased by about 120–289 m and the MAAR of Fairweather glacier, Lituya glacier, and Desolation glacier decreased by about 3–6%. In contrast, MSLA and MAAR of Crillon glacier decreased by about 70 m and increased by about 1%, respectively. Glacier elevation change results showed that 7.7 m, 4.6 m and 1.5 m of mean thinning change were observed, respectively, on Fairweather glacier, Lituya glacier, and Desolation glacier. However, 7 m and 0.65 m of mean thickening were, respectively, experienced on Cascade glacier and Crillon glacier in the same period. Results from the study indicated that glacier retreat (Fairweather glacier, Lituya glacier, and Desolation glacier) affected by higher temperatures probably dominates with over-increased precipitation. However, increasing debris cover on the glacier surface can also modify the glacier dynamic, resulting in a different response to global warming.     

基于遥感的祁连山东部冷龙岭冰川变化研究

利用1970年的地形图,1995、1999、2002和2009年的Landsat\|TM/ETM遥感影像,通过遥感图像处理和GIS技术对祁连山冷龙岭地区的冰川变化进行研究。结果表明：研究区的冰川面积1990年以来变化显著,1995年冰川面积比1970年减少了13.79%,1999年冰川面积比1995年减少了21.96%,2002年冰川面积比1999年减少了10.54%,2009年冰川面积比2002年减少了6.35%。选取研究区不同规模的18条典型冰川进行面积长度的变化分析,总体情况与前面一致。