scholarly journals A regionally resolved inventory of High Mountain Asia surge-type glaciers, derived from a multi-factor remote sensing approach

2021 ◽  
Author(s):  
Gregoire Guillet ◽  
Owen King ◽  
Mingyang Lv ◽  
Sajid Ghuffar ◽  
Douglas Benn ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Google Earth ◽  
Surface Velocity ◽  
High Mountain ◽  
Abstract Knowledge ◽  
High Resolution Imagery ◽  
Self Organized Criticality ◽  
Glacier Surges ◽  
Very High Resolution Imagery ◽  
The Impact

Abstract. Knowledge about the occurrence and characteristics of surge-type glaciers is crucial due to the impact of surging on glacier melt and glacier related hazards. One of the "super-clusters" of surge-type glaciers is the mountains of Asia. However, no consistent region-wide inventory of surge-type glaciers in High Mountain Asia exists. We present a regionally resolved inventory of surge-type glaciers based on their behaviour across High Mountain Asia between 2000 and 2018. We identify surge-type behaviour from surface velocity, elevation and feature change patterns using a multi-factor remote sensing approach that combines yearly ITS_LIVE velocity data, DEM differences and very-high resolution imagery (Bing Maps, Google Earth). Out of the ≈ 95000 glaciers in HMA, we identified 666 that show diagnostic surge-type glacier behaviour between 2000 and 2018, which are mainly found in the Karakoram (223) and the Pamir regions (223). The total area covered by the 666 surge-type glaciers represents 19.5 % of the glacierized area in Randolph Glacier Inventory (RGI) V6.0 polygons in HMA. Across all regions of HMA, the surge-affected area within glacier complexes displays a significant power law dependency with glacier length. We validate 107 previously identified glaciers as surge-type and newly identify 491 glaciers. We finally discuss the possibility of self-organized criticality in glacier surges.

scholarly journals More dynamic than expected: an updated survey of surging glaciers in the Pamir

2020 ◽  
Vol 12 (4) ◽  
pp. 3161-3176
Author(s):  
Franz Goerlich ◽  
Tobias Bolch ◽  
Frank Paul
Keyword(s):  
Google Earth ◽  
Strong Increase ◽  
High Mountain ◽  
Systematic Analysis ◽  
High Resolution Imagery ◽  
Digital Elevation ◽  
Western Kunlun ◽  
Glacier Surges ◽  
Very High Resolution Imagery ◽  
Very High

Abstract. The investigation of surging glaciers using remote sensing has recently seen a strong increase as freely available satellite data and digital elevation models (DEMs) can provide detailed information about surges that often take place in remote and inaccessible regions. Apart from analysing individual surges, satellite information is increasingly used to collect valuable data on surging glaciers. Related inventories have recently been published for several regions in High Mountain Asia including the Karakoram or parts of the Pamir and western Kunlun Shan, but information for the entire Pamir is solely available from a historic database listing about 80 glaciers with confirmed surges. Here we present an updated inventory of confirmed glacier surges for the Pamir that considers results from earlier studies and is largely based on a systematic analysis of Landsat image time series (1988 to 2018), very high-resolution imagery (Corona, Hexagon, Bing Maps, Google Earth) and DEM differences. Actively surging glaciers (e.g. with advancing termini) were identified from animations and flicker images and the typical elevation change patterns (lowering in an upper reservoir zone and thickening further down in a receiving zone). In total, we identified 206 spatially distinct surges within 186 glacier bodies mostly clustered in the northern and western part of the Pamir. Where possible, minimum and maximum glacier extents were digitised, but often interacting tributaries made a clear separation challenging. Most surging glaciers (n=70) are found in the larger size classes (>10 km2), but two of them are very small (<0.5 km2). We also found several surges where the length of the glacier increased by more than 100 %. The created datasets are available at: https://doi.org/10.1594/PANGAEA.914150 (Goerlich et al., 2020).

scholarly journals Distinguishing Glaciers between Surging and Advancing by Remote Sensing: A Case Study in the Eastern Karakoram

2020 ◽  
Vol 12 (14) ◽  
pp. 2297 ◽  
Author(s):  
Mingyang Lv ◽  
Huadong Guo ◽  
Jin Yan ◽  
Kunpeng Wu ◽  
Guang Liu ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Google Earth ◽  
High Mountain ◽  
Glacier Mass Balance ◽  
Visual Interpretation ◽  
Stable Mode ◽  
Optical Images ◽  
Digital Elevation ◽  
Glacier Surges ◽  
Elevation Model

The Karakoram has had an overall slight positive glacier mass balance since the end of 20th century, which is anomalous given that most other regions in High Mountain Asia have had negative changes. A large number of advancing, retreating, and surging glaciers are heterogeneously mixed in the Karakoram increasing the difficulties and inaccuracies to identify glacier surges. We found two adjacent glaciers in the eastern Karakoram behaving differently from 1995 to 2019: one was surging and the other was advancing. In order to figure out the differences existing between them and the potential controls on surges in this region, we collected satellite images from Landsat series, ASTER, and Google Earth, along with two sets of digital elevation model. Utilizing visual interpretation, feature tracking of optical images, and differencing between digital elevation models, three major differences were observed: (1) the evolution profiles of the terminus positions occupied different change patterns; (2) the surging glacier experienced a dramatic fluctuation in the surface velocities during and after the event, while the advancing glacier flowed in a stable mode; and (3) surface elevation of the surging glacier decreased in the reservoir and increased in the receiving zone. However, the advancing glacier only had an obvious elevation increase over its terminus part. These differences can be regarded as standards for surge identification in mountain ranges. After combining the differences with regional meteorological conditions, we suggested that changes of thermal and hydrological conditions could play a role in the surge occurrence, in addition, geomorphological characteristics and increasing warming climate might also be part of it. This research strongly contributes to the literatures of glacial motion and glacier mass change in the eastern Karakoram through remote sensing.

scholarly journals More dynamic than expected: An updated survey of surging glaciers in the Pamir

2020 ◽  
Author(s):  
Franz Goerlich ◽  
Tobias Bolch ◽  
Frank Paul
Keyword(s):  
Strong Increase ◽  
High Mountain ◽  
Elevation Change ◽  
Systematic Analysis ◽  
High Resolution Imagery ◽  
Digital Elevation ◽  
Western Kunlun ◽  
Glacier Surges ◽  
Very High Resolution Imagery ◽  
Very High

Abstract. The investigation of surging glaciers using remote sensing has recently seen a strong increase as freely available satellite data and digital elevation models (DEMs) can provide detailed information about surges that often take place in remote or inaccessible regions. Apart from analysing individual surges, satellite information is increasingly used to collect capable data on surging glaciers. Related inventories have recently been published for several regions in High Mountain Asia including the Karakoram, parts of the Pamir and western Kunlun Shan, but information for the entire Pamir is solely available from a historic database listing about 80 glaciers with confirmed surges. Here we present an updated inventory of confirmed glacier surges for the Pamir that considers results from earlier studies and is based on a systematic analysis of Landsat image time series (1988 to 2018) and DEM differences. Actively surging glaciers were identified from animations, flicker images and the typical elevation change patterns. Selected historic and contemporary very high-resolution imagery were used to confirm surges. In total, we identified 206 spatially distinct surges within 186 glacier bodies, mostly clustered in the northern and central part of the Pamir. Where possible, minimum and maximum glacier extents were digitized, but often interacting tributaries made a clear separation challenging. Most surging glaciers (n = 70) are found in the larger size classes (> 10 km2), but two of them are very small (

Assessing and monitoring the vulnerability to drought and climate anomalies of Mediterranenan oak forests by using NDVI

2020 ◽  
Author(s):  
Maria Castellaneta ◽  
Angelo Rita ◽  
J. Julio Camarero ◽  
Michele Colangelo ◽  
Angelo Nolè ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Time Series ◽  
Tree Mortality ◽  
Vegetation Index ◽  
Google Earth ◽  
Oak Forests ◽  
Summer Drought ◽  
Area Index ◽  
Ndvi Time Series ◽  
The Impact

&lt;p&gt;Several die-off episodes related to heat weaves and drought spells have evidenced the high vulnerability of Mediterranean oak forests. These events consisted in the loss in tree vitality and manifested as growths decline, elevated crown transparency (defoliation) and rising tree mortality rate. In this context, the changes in vegetation productivity and canopy greenness may represent valuable proxies to analyze how extreme climatic events trigger forest die-off. Such changes in vegetation status may be analyzed using remote-sensing data, specifically multi-temporal spectral information. For instance, the Normalized Difference Vegetation Index (NDVI) measures changes in vegetation greenness and is a proxy of changes in leaf area index (LAI), forest aboveground biomass and productivity. In this study, we analyzed the temporal patterns of vegetation in three Mediterranean oak forests showing recent die-off in response to the 2017 severe summer drought. For this purpose, we used an open-source platform (Google Earth Engine) to extract collections of MODIS NDVI time-series from 2000 to 2019. The analysis of both NDVI trends and anomalies were used to infer differential patterns of vegetation phenology among sites comparing plots where most trees were declining and showed high defoliation (test) versus plots were most trees were considered healthy (ctrl) and showed low or no defoliation. Here we discuss: i) the likely offset in NDVI time-series between test- versus ctrl- sites; and ii) the impact of summer droughts &amp;#160;on NDVI.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: climate change, forest vulnerability, time series, remote sensing.&lt;/p&gt;

Using remote sensing to monitor peatland fire occurrence and recovery

2020 ◽  
Author(s):  
Kirsten Lees ◽  
Josh Buxton ◽  
Chris Boulton ◽  
Tim Lenton
Keyword(s):  
Remote Sensing ◽  
Great Britain ◽  
Management Practice ◽  
Google Earth ◽  
Small Scale ◽  
Fire Occurrence ◽  
Wildfire Occurrence ◽  
Visual Record ◽  
Remote Sensing Methods ◽  
The Impact

&lt;p&gt;Many peatland areas in Great Britain are managed as grouse moors, with regular burns as part of management practice to encourage heather growth. Remote sensing has the potential to monitor the size, location, and impact of these burns using new fine resolution satellites such as Sentinel-2. Google Earth Engine allows large areas to be analysed at small scale over several years, building up a visual record of fire occurrence. This study uses satellite data to map managed burns on several areas of moorland around Great Britain, and uses remote sensing methods to assess the impact of this management strategy on vegetation cover. The project also considers how areas subject to managed burns react to wildfire occurrence, with the 2018 Saddleworth wildfire as a case study.&lt;/p&gt;

Early 21st-century glacier surface mass balance across High Mountain Asia derived from remote sensing

2020 ◽  
Author(s):  
Evan Miles ◽  
Michael McCarthy ◽  
Amaury Dehecq ◽  
Marin Kneib ◽  
Stefan Fugger ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Mass Balance ◽  
Surface Velocity ◽  
High Mountain ◽  
Surface Mass Balance ◽  
Equilibrium Line Altitude ◽  
Glacier Surface ◽  
Surface Mass ◽  
Early 21St Century ◽  
Debris Cover

&lt;p&gt;Glaciers in High Mountain Asia have experienced intense scientific scrutiny in the past decade due to their hydrological and societal importance. The explosion of freely-available satellite observations has greatly advanced our understanding of their thinning, motion, and overall mass losses, and it has become clear that they exhibit both local and regional variations due to debris cover, surging and climatic regime. However, our understanding of glacier accumulation and ablation rates is limited to a few individual sites, and altitudinal surface mass balance is essentially unknown across the vast region.&lt;/p&gt;&lt;p&gt;Here we combine recent assessments of ice thickness and surface velocity to correct observed glacier thinning rates for mass redistribution in a flowband framework to derive the first estimates of altitudinal glacier surface mass balance across the region. We first evaluate our results at the glacier scale with all available glaciological field measurements (27 glaciers), then analyze 4665 glaciers (we exclude surging and other anomalous glaciers) comprising 43% of area and 36% of mass for glaciers larger than 2 km&lt;sup&gt;2&lt;/sup&gt; in the region. The surface mass balance results allow us to determine the equilibrium line altitude for each glacier for the period 2000-2016.&amp;#160; We then aggregate our altitudinal and hypsometric surface mass balance results to produce idealised profiles for distinct subregions, enabling us to consider the subregional heterogeneity of mass balance and the importance of debris-covered ice for the region&amp;#8217;s overall ablation.&lt;/p&gt;&lt;p&gt;We find clear patterns of ELA variability across the region. &amp;#160;9% of glaciers accumulate mass over less than 10% of their area on average for the study period. These doomed&amp;#160; glaciers are concentrated in Nyainqentanglha, which also has the most negative mass balance of the subregions, whereas accumulation area ratios of 0.7-0.9 are common for glaciers in the neutral-balance Karakoram and Kunlun Shan. We find that surface debris extent is negatively correlated with ELA, explaining up to 1000 m of variability across the region and reflecting the importance of avalanching as a mass input for debris-covered glaciers at lower elevations. However, in contrast with studies of thinning rates alone, we find a clear melt reduction for low-elevation debris-covered glacier areas, consistent across regions, largely resolving the &amp;#8216;debris cover anomaly&amp;#8217;.&amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;Our results provide a comprehensive baseline for the health of the High Asian ice reservoirs in the early 21&lt;sup&gt;st&lt;/sup&gt; Century. The estimates of altitudinal surface mass balance and ELAs will additionally enable novel strategies for the calibration of glacier and hydrological models. Finally, our results emphasize the potential of combined remote-sensing observations to understand the environmental factors and physical processes responsible for High Asia&amp;#8217;s heterogeneous patterns of recent glacier evolution.&lt;/p&gt;

Glaciers of Grandes Jorasses: an open-air laboratory for glacier monitoring systems development

2020 ◽  
Author(s):  
Niccolò Dematteis ◽  
Daniele Giordan ◽  
Fabrizio Troilo
Keyword(s):  
Remote Sensing ◽  
Image Correlation ◽  
Surface Velocity ◽  
Monitoring Systems ◽  
High Mountain ◽  
European Alps ◽  
Total Station ◽  
Research Activities ◽  
Close Range ◽  
Glacial Complex

&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Glaciological phenomena can have a strong impact on human activities in terms of hazards and freshwater supply. Therefore, a scientific observation is fundamental to investigate their current state and recent evolution. To this aim, experimenting innovative scientific survey methodologies and equipment is of primary importance. Strong efforts in this field have been spent in the glacial complex of the Grandes Jorasses massif (Mont Blanc area), where several ice break-offs glacial outburst triggered from the Planpincieux Glacier snout and the Whymper Serac and threatened the underling Planpincieux valley in the past. From 2009, the glacial complex has become an open filed laboratory where a wide set of close-range remote sensing survey systems have been developed and applied to investigate the glacial state and dynamics.&lt;/p&gt;&lt;p&gt;Two continuous monoscopic time-lapse cameras observe the Planpincieux Glacier since 2013. Digital image correlation is applied to the photographs to measure the surface kinematics at different level of detail. During the monitoring, image analysis techniques allowed at classifying the instability processes of the terminus and at estimating the volume of the break-off events. Such investigation revealed the presence of possible break-off precursors and a monotonic relationship between glacier velocity and break-off volume, which might help for risk evaluation.&lt;/p&gt;&lt;p&gt;A robotised total station (RTS) is active since 2009 to monitor the Whymper Serac velocity (Grandes Jorasses Glacier). The operative distance between the total station and targets is approximately 5000 m. A network of several prisms is installed onto the serac, but the extreme conditions related to the high-mountain environment force to replace periodically the stakes that are lost. Besides the RTS, a monoscopic camera acquires hourly images of the serac for surface velocity measurements.&lt;/p&gt;&lt;p&gt;In addition to the permanent monitoring systems, surveys with four different terrestrial interferometric radars have been conducted in the Planpincieux Glacier between 2013 and 2019. Helicopter-borne LiDAR and terrestrial laser scanner provided the DEM of the Planpincieux Glacier in 2014 and 2015 respectively. A sequence of six DEMs has been also produced by aerial and UAV structure from motion in the time span 2017-2019. Finally, a helicopter ground penetrating radar campaign was conducted in 2013 to evaluate the thickness of the Planpincieux Glacier and Whymper Serac.&lt;/p&gt;&lt;p&gt;For what concerns the mountain glaciers, the survey activity conducted in the Grandes Jorasses massif since 2009 is probably one the most intensive and variegated in European Alps. This makes such an environment an open-air laboratory for experimenting close-range remote sensing monitoring systems that it is ready for new research activities and monitoring solutions development.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals GIS and Remote Sensing Analysis of the Impact of Land use Land Cover Change on Forest Degradation: Evidence from the Central Part of Taraba State, Nigeria

2021 ◽  
pp. 27-39
Author(s):  
Umar Jauro Abba ◽  
Adewuyi Taiye ◽  
Yusuf Mohammed Bakoji ◽  
Bashir Babanyaya Mohammed ◽  
Adamu Auwal Umar ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Land Cover ◽  
Local Governments ◽  
Early Stage ◽  
Central Zone ◽  
Google Earth ◽  
Forest Environment ◽  
Gis And Remote Sensing ◽  
Bare Land ◽  
The Impact

Forest is a fundamental, significant, and valuable component of a sustainable environment. Ecosystem services, biodiversity development, and economic growth in any nation depend on the proficient use of forests and their resources. However, deforestation has remained the single most important environmental phenomenon threatening the existence of the forest environment in Nigeria. This study was carried out to assess the exploitation of forestland in the central zone of Taraba state using GIS and remote sensing techniques. The satellite imageries used are Lands at imageries of 2006, 2012, and 2018. Ground Control points (GCPs) were obtained from Google earth to validate the coordinates of the classified imageries. The result obtained from 2006 classification showed that thick forest occupied the total of 1685448.99 ha equivalent to 80.38% and was the highest land cover suffering a decline in the area amounting to 694696 ha which equals to 33.13% in 2018. The pattern of land cover changes at the early stage was restricted to dissection and perforation in 2006. A remarkable expansion of bare land patches accompanied by total attrition of thick forest was identified due North in Bali local government area as compared to Gashaka and Kurmi local governments that have fragmented and little shrinking pattern of changes from 6.87% in 2006 to 37.65% in 2018. This shows that; as bare land increases, thick forests keep on decreasing within thirteen (13) years. It was recommended that increased reforestation efforts, sensitization and periodical campaigns against deforestation, and redesign of the existing forestry laws by the state government to curtail incessant incidents of deforestation in the study area be undertaken.

scholarly journals Effect of Satellite Temporal Resolution on Long-Term Suspended Particulate Matter in Inland Lakes

2019 ◽  
Vol 11 (23) ◽  
pp. 2785 ◽  
Author(s):  
Zhigang Cao ◽  
Ronghua Ma ◽  
Hongtao Duan ◽  
Kun Xue ◽  
Ming Shen
Keyword(s):  
Remote Sensing ◽  
Water Quality ◽  
Particulate Matter ◽  
Temporal Resolution ◽  
Suspended Particulate Matter ◽  
Google Earth ◽  
Inland Lakes ◽  
Suspended Particulate ◽  
The Impact

The temporal resolution of satellite determines how well remote sensing products represent changes in the lake environments and influences the practical applications by end-users. Here, a resampling method was used to reproduce the suspended particulate matter (SPM) dataset in 43 large lakes (>50 km2) on the eastern China plain during 2003–2017 at different temporal resolutions using MODIS Aqua (MODISA) based on Google Earth Engine platform, then to address the impact of temporal resolution on the long-term SPM dataset. Differences between the MODISA-derived and reproduced SPM dataset at longer temporal resolution were higher in the areas with large water dynamics. The spatial and temporal distributions of the differences were driven by unfavorable observation environments during satellite overpasses such as high cloud cover, and rapid changes in water quality, such as water inundation, algae blooms, and macrophytes. Furthermore, the annual mean difference in SPM ranged from 5–10% when the temporal difference was less than 10 d, and the differences in summer and autumn were higher than that of other seasons and surpassed 20% when the temporal resolution was more than 16 d. To assure that difference were less than 10% for long-term satellite-derived SPM datasets, the minimal requirement of temporal resolution should be within 5 d for most of the inland lakes and 3 d for lakes with large changes in water quality. This research can be used to not only evaluate the reliability of historically remote sensing products but also provide a reference for planning field campaigns and applying of high spatial resolution satellite missions to monitor aquatic systems in the future.

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