scholarly journals The use of remote-sensing data for mass-balance studies at Mýrdalsjökull ice cap, Iceland

2006 ◽  
Vol 52 (179) ◽  
pp. 565-573 ◽  
Author(s):  
Julia Jaenicke ◽  
Christoph Mayer ◽  
Kilian Scharrer ◽  
Ulrich Münzer ◽  
Agúst Gudmundsson
Keyword(s):  
Mass Balance ◽  
Satellite Images ◽  
Inverse Function ◽  
Remote Sensing Data ◽  
Late Summer ◽  
Radar Data ◽  
Synthetic Aperture Radar Data ◽  
Envisat Asar ◽  
Radar Images ◽  
Optical Satellite Images

AbstractA series of satellite images of Mýrdalsjökull, Iceland, was analyzed in view of their value for mass-balance investigations. A combination of optical satellite images from the ASTER sensor and synthetic aperture radar data from ERS-2 and Envisat ASAR proved very useful. The glacier margin of Mýrdalsjökull was delineated on ASTER images from summer and winter 2004. With a time series of summer ASAR images it was possible to monitor the temporal and spatial development of the transient snowline (TSL) throughout the year 2004, as well as the firn line (FL) at the end of the balance year. An ‘inverse’ function was applied to visually enhance detail in the radar imagery. Winter radar images were not useful for mass-balance observations because of frequent surface melting, which prevented the transparency of the snow cover for C-band microwaves. Interannual mass-balance fluctuations were observed by comparing three radar images acquired in late summer 1998, 1999 and 2004 respectively. These fluctuations follow the same trend as the annual mean air temperature which shows a strong increasing trend between 1999 and 2004. An accumulation-area ratio of <0.43 was determined for 2004, indicating clear negative mass-balance conditions. Monitoring the TSL-FL with radar summer images for mass-balance studies, rather than the equilibrium line (EL), is suggested for large ice caps in maritime climates.

scholarly journals NN-Based Prediction of Sentinel-1 SAR Image Filtering Efficiency

Geosciences ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 290 ◽  
Author(s):  
Rubel ◽  
Lukin ◽  
Rubel ◽  
Egiazarian
Keyword(s):  
Neural Network ◽  
Image Quality ◽  
Real Life ◽  
Remote Sensing Data ◽  
Radar Data ◽  
Quality Metrics ◽  
Radar Images ◽  
Filtering Efficiency ◽  
Trained Neural Network ◽  
Synthetic Aperture Radars

Images acquired by synthetic aperture radars are degraded by speckle that prevents efficient extraction of useful information from radar remote sensing data. Filtering or despeckling is a tool often used to improve image quality. However, depending upon image and noise properties, the quality of improvement can vary. Besides, a quality can be characterized by different criteria or metrics, where visual quality metrics can be of value. For the case study of discrete cosine transform (DCT)based filtering, we show that improvement of radar image quality due to denoising can be predicted in a simple and fast way, especially if one deals with particular type of radar data such as images acquired by Sentinel-1. Our approach is based on application of a trained neural network that, in general, might have a different number of inputs (features). We propose a set of features describing image and noise statistics from different viewpoints. From this set, that contains 28 features, we analyze different subsets and show that a subset of the 13 most important and informative features leads to a very accurate prediction. Test image generation and network training peculiarities are discussed. The trained neural network is then tested using different verification strategies. The results of the network application to test and real-life radar images are presented, demonstrating good performance for a wide set of quality metrics.

scholarly journals Utility of late summer transient snowline migration rate on Taku Glacier, Alaska

2011 ◽  
Vol 5 (4) ◽  
pp. 1127-1133 ◽  
Author(s):  
M. Pelto
Keyword(s):  
Mass Balance ◽  
Migration Rate ◽  
Satellite Images ◽  
Snow Water Equivalent ◽  
Late Summer ◽  
Ablation Rate ◽  
Field Observations ◽  
Balance Assessment ◽  
Snow Water ◽  
The Mean

Abstract. On Taku Glacier, Alaska a combination of field observations of snow water equivalent (SWE) from snowpits and probing in the vicinity of the transient snowline (TSL) are used to quantify the mass balance gradient. The balance gradient derived from the TSL and SWE measured in snowpits at 1000 m from 1998–2010 ranges from 2.6–3.8 mm m−1. Probing transects from 950 m–1100 m directly measure SWE and yield a slightly higher balance gradient of 3.3–3.8 mm m−1. The TSL on Taku Glacier is identified in MODIS and Landsat 4 and 7 Thematic Mapper images for 31 dates during the 2004–2010 period to assess the consistency of its rate of rise and reliability in assessing ablation for mass balance assessment. For example, in 2010, the TSL was 750 m on 28 July, 800 m on 5 August, 875 m on 14 August, 925 m on 30 August, and 975 m on 20 September. The mean observed probing balance gradient was 3.3 mm m−1, combined with the TSL rise of 3.7 m day−1 yields an ablation rate of 12.2 mm day−1 from mid-July to mid-Sept, 2010. The TSL rise in the region from 750–1100 m on Taku Glacier during eleven periods each covering more than 14 days during the ablation season indicates a mean TSL rise of 3.7 m day−1, the rate of rise is relatively consistent ranging from 3.1 to 4.4 m day−1. This rate is useful for ascertaining the final ELA if images or observations are not available near the end of the ablation season. The mean ablation from 750–1100 m during the July–September period determined from the TSL rise and the observed balance gradient is 11–13 mm day−1 on Taku Glacier during the 2004–2010 period. The potential for providing an estimate of bn from TSL observations late in the melt season from satellite images combined with the frequent availability of such images provides a means for efficient mass balance assessment in many years and on many glaciers.

scholarly journals Spatio-temporal changes in glacier-wide mass balance quantified by optical remote sensing on 30 glaciers in the French Alps for the period 1983–2014

2016 ◽  
Vol 62 (236) ◽  
pp. 1153-1166 ◽  
Author(s):  
ANTOINE RABATEL ◽  
JEAN PIERRE DEDIEU ◽  
CHRISTIAN VINCENT
Keyword(s):  
Remote Sensing ◽  
Mass Balance ◽  
Satellite Images ◽  
Optical Remote Sensing ◽  
European Alps ◽  
Mass Balances ◽  
Glacier Surface ◽  
Uncertainty Range ◽  
French Alps ◽  
Optical Satellite Images

AbstractRemote sensing is a powerful method to reconstruct annual mass-balance series over past decades by exploiting archives of available images, as well as to study glaciers in inaccessible regions. We present the application of a methodological framework based only on optical satellite images to retrieve glacier-wide annual mass balances for 30 glaciers in the French Alps. The glacier-wide annual mass balance for the period 1983–2014 was reconstructed by combining changes in glacier volumes computed from remote-sensing derived DEMs with annual measurements of the snow line altitude on satellite images. Data from direct observations on two of the glaciers confirmed the accuracy of the annual mass balances quantified by remote sensing with an average difference of ~0.3 m w.e., within the uncertainty range of the methods. Our results confirm the significant increase in mass loss since the early 2000s, with a difference >1 m w.e. a−1 between the periods 1983–2002 and 2003–14. The region-wide mass balance for the French Alps over the period 1979–2011 was −0.66 ± 0.27 m w.e. a−1, close to that of the European Alps. We also show that changes in glacier surface area or length are not representative of changes in mass balance at the scale of a few decades.

scholarly journals Worldwide widespread decadal-scale decrease of glacier speed revealed using repeat optical satellite images

2011 ◽  
Vol 5 (5) ◽  
pp. 3025-3051 ◽  
Author(s):  
T. Heid ◽  
A. Kääb
Keyword(s):  
Mass Balance ◽  
Satellite Images ◽  
Glacier Mass Balance ◽  
Positive Mass ◽  
Alaska Range ◽  
Ice Cap ◽  
Decadal Scale ◽  
Glacier Dynamics ◽  
The World ◽  
Optical Satellite Images

Abstract. Matching of repeat optical satellite images to derive glacier velocities is an approach that is much used within glaciology. Lately, focus has been put into developing, improving, automating and comparing different image matching methods. This makes it now possible to investigate glacier dynamics within large regions of the world and also between regions to improve knowledge about glacier dynamics in space and time. In this study we investigate whether the negative glacier mass balance seen over large parts of the world has caused the glaciers to change their speeds. The studied regions are Pamir, Caucasus, Penny Ice Cap, Alaska Range and Patagonia. In addition we derive speed changes for Karakoram, a region assumed to have positive mass balance and that contains many surge-type glaciers. We find that the mapped glaciers in the five regions with negative mass balance have decreased their speeds over the last decades, Pamir by 43 % in average per decade, Caucasus by 8 % in average per decade, Penny Ice Cap by 25 % in average per decade, Alaska Range by 11 % in average per decade and Patagonia by 20 % in average per decade. Glaciers in Karakoram have generally increased their speeds, but surging glaciers and glaciers with flow instabilities are most prominent in this area.

scholarly journals Improved estimation of the mass balance of glaciers draining into the Amundsen Sea sector of West Antarctica from the CECS/NASA 2002 campaign

2004 ◽  
Vol 39 ◽  
pp. 231-237 ◽  
Author(s):  
Eric Rignot ◽  
Robert H. Thomas ◽  
Pannir Kanagaratnam ◽  
Gino Casassa ◽  
Earl Frederick ◽  
...  
Keyword(s):  
Mass Balance ◽  
Radar Data ◽  
Snow Accumulation ◽  
West Antarctica ◽  
Amundsen Sea ◽  
Synthetic Aperture Radar Data ◽  
Ice Shelves ◽  
Flow Acceleration ◽  
Elevation Data ◽  
Radio Echo Sounding

AbstractIn November–December 2002, a joint airborne experiment by Centro de Estudios Cientifícos and NASA flew over the Antarctic ice sheet to collect laser altimetry and radio-echo sounding data over glaciers flowing into the Amundsen Sea. A P-3 aircraft on loan from the Chilean Navy made four flights over Pine Island, Thwaites, Pope, Smith and Kohler glaciers, with each flight yielding 1.5–2 hours of data. The thickness measurements reveal that these glaciers flow into deep troughs, which extend far inland, implying a high potential for rapid retreat. Interferometric synthetic aperture radar data (InSAR) and satellite altimetry data from the European Remote-sensing Satellites (ERS-1/-2) show rapid grounding-line retreat and ice thinning of these glaciers. Using the new thickness data, we have reevaluated glacier fluxes and the present state of mass balance, which was previously estimated using ice thicknesses deduced largely from inversion of elevation data assuming hydrostatic equilibrium. The revised total ice discharge of 241 ± 5km3 a–1 exceeds snow accumulation by 81 ± 17 km3 a–1 of ice, equivalent to a sea-level rise of 0.21 ± 0.04 mma–1. This magnitude of ice loss is too large to be caused by atmospheric forcing and implies dynamic thinning of the glaciers. This is confirmed by ice-flow acceleration observed with InSAR. We attribute the flow acceleration and ice thinning to enhanced bottom melting of the ice shelves by a warmer ocean, which reduces buttressing of the glaciers, and in turn accelerates them out of balance.

scholarly journals Mass balance of Devon Ice Cap, Canadian Arctic

2007 ◽  
Vol 46 ◽  
pp. 249-254 ◽  
Author(s):  
Andrew Shepherd ◽  
Zhijun Du ◽  
Toby J. Benham ◽  
Julian A. Dowdeswell ◽  
Elizabeth M. Morris
Keyword(s):  
Mass Balance ◽  
Sea Level ◽  
Canadian Arctic ◽  
Radar Data ◽  
Synthetic Aperture ◽  
Interferometric Synthetic Aperture Radar ◽  
Synthetic Aperture Radar Data ◽  
Sea Levels ◽  
Ice Cap ◽  
Devon Ice Cap

AbstractInterferometric synthetic aperture radar data show that Devon Ice Cap (DIC), northern Canada, is drained through a network of 11 glacier systems. More than half of all ice discharge is through broad flows that converge to the southeast of the ice cap, and these are grounded well below sea level at their termini. A calculation of the ice-cap mass budget reveals that the northwestern sector of DIC is gaining mass and that all other sectors are losing mass. We estimate that a 12 489 km2 section of the main ice cap receives 3.46±0.65 Gt of snowfall each year, and loses 3.11±0.21 Gt of water through runoff, and 1.43±0.03 Gt of ice through glacier discharge. Altogether, the net mass balance of DIC is –1.08±0.67 Gt a–1. This loss corresponds to a 0.003 mma–1 contribution to global sea levels, and is about half the magnitude of earlier estimates.

scholarly journals Monitoring Vegetation Cover Changes by Sentinel-1 Radar Images Using Random Forest Classification Method

2021 ◽  
Vol 1 (2) ◽  
Author(s):  
Van Anh TRAN ◽  
Thi Le LE ◽  
Nhu Hung NGUYEN ◽  
Thanh Nghi LE ◽  
Hong Hanh TRAN
Keyword(s):  
Vegetation Cover ◽  
Satellite Images ◽  
Satellite Image ◽  
Mekong Delta ◽  
Asian Country ◽  
Climatic Conditions ◽  
Random Forest Classification ◽  
Remote Sensing Technique ◽  
Radar Images ◽  
Optical Satellite Images

Vietnam is an Asian country with hot and humid tropical climate throughout the year. Forestsaccount for more than 40% of the total land area and have a very rich and diverse vegetation.Monitoring the changes in the vegetation cover is obviously important yet challenging, considering suchlarge varying areas and climatic conditions. A traditional remote sensing technique to monitor thevegetation cover involves the use of optical satellite images. However, in presence of the cloud cover,the analyses done using optical satellite image are not reliable. In such a scenario, radar images are auseful alternative due to the ability of radar pulses in penetrating through the clouds, regardless of day ornight. In this study, we have used multi temporal C band satellite images to monitor vegetation coverchanges for an area in Dau Tieng and Ben Cat districts of Binh Duong province, Mekong Delta,Vietnam. With a collection of 46 images between March 2015 and February 2017, the changes of fiveland cover types including vegetation loss and replanting in 2017 were analyzed by selecting two cases,using 9 images in the dry season of 3 years 2015, 2016 and 2017 and using all of 46 images to conductRandom Forest classifier with 100, 200, 300 and 500 trees respectively. The result in which the modelwith nine images and 300 trees gave the best accuracy with an overall accuracy of 98.4% and a Kappaof 0.97. The results demonstrated that using VH polarization, Sentinel-1 gives quite a good accuracy forvegetation cover change. Therefore, Sentinel-1 can also be used to generate reliable land cover mapssuitable for different applications.

scholarly journals Using remote sensing for monitoring of reforestation in boreal forest

2019 ◽  
Author(s):  
А.А. Карпов ◽  
А.П. Богданов ◽  
Н.Р. Пирцхалава-Карпова ◽  
Н.А. Демина
Keyword(s):  
Optical Sensors ◽  
Satellite Images ◽  
Radar Data ◽  
Burned Areas ◽  
Advantages And Disadvantages ◽  
Radar Images ◽  
Conducting Research ◽  
The Cost ◽  
Radar Data Processing ◽  
Optical Radar

Оценка лесовосстановления по спутниковым снимкам и создание системы мониторинга является важной задачей на сегодняшний день. Российские и зарубежные ученые проводят исследования в этом направлении, но анализ лесовосстановления является сложной темой исследования в отличие от выявления вырубок и гарей по спутниковым снимкам. Лесовосстановление также является сложным, многофакторным процессом, зависящим от множества факторов. Данная статья описывает мировой опыт создания различных методик для мониторингалесовосстановления, используя различные подходы анализа данных и сенсоры, установленные на спутниках. В рамках статьи рассмотрено применение оптических, радарных снимков и данных, полученных с лидарных сенсоров. Это попытка структурировать накопленный опыт в данной сфере и сгруппировать разработанные методики для анализа их преимуществ и недостатков. Тип сенсора определяет длительность периода мониторинга. Радарные данные позволяют определять процесс лесовосстановления до 60 лет в отличие от оптических сенсоров, которые имеют значительно меньший период оценки лесовосстановления. Применение радарных данных может быть ограничено стоимостью работы и сложностью обработки радарных данных, поэтому использование тех или иных методик может иметь финансовые ограничения. Данный обзор показывает все основные методы оценки лесовосстановления. Assessment of reforestation using satellite images and creation of a monitoring system is an important task today. Russian and foreign scientists are conducting research in this direction, but the analysis of reforestation is a complex topic of research in contrast to the detection of cuttings and burned areas by satellite images. The process of reforestation is a complex, multi-factor process depending on many factors. This article describes the world experience of creating different methods for monitoring forest regeneration and uses different approaches to data analysis and sensors installed on satellites. In the framework of article was considered using of optical, radar images and data obtained from lidar sensors. This is an attempt to structure the accumulated experience in this field and group the developed methods to analyze their advantages and disadvantages. Data from different sensors have different monitoring period. Radar data allow determining the process of reforestation up to 60 years in contrast to optical sensors, which have a much shorter period of reforestation assessment. The using of radar data were limited by the cost of operation and complexity of radar data processing and using of certain techniques may have financial limitations. This review showed all the main methods of assessment of reforestation.

scholarly journals Detection of Liquefaction Phenomena from the 2017 Pohang (Korea) Earthquake Using Remote Sensing Data

2019 ◽  
Vol 11 (18) ◽  
pp. 2184 ◽  
Author(s):  
Baik ◽  
Son ◽  
Kim
Keyword(s):  
Satellite Images ◽  
Remote Sensing Data ◽  
Short Wave ◽  
Landsat 8 ◽  
Content Increase ◽  
Infrared Band ◽  
Water Index ◽  
Before And After ◽  
Optical Satellite Images ◽  
Sentinel 2

On 15 November 2017, liquefaction phenomena were observed around the epicenter after a 5.4 magnitude earthquake occurred in Pohang in southeast Korea. In this study, we attempted to detect areas of sudden water content increase by using SAR (synthetic aperture radar) and optical satellite images. We analyzed coherence changes using Sentinel-1 SAR coseismic image pairs and analyzed NDWI (normalized difference water index) changes using Landsat 8 and Sentinel-2 optical satellite images from before and after the earthquake. Coherence analysis showed no liquefaction-induced surface changes. The NDWI time series analysis models using Landsat 8 and Sentinel-2 optical images confirmed liquefaction phenomena close to the epicenter but could not detect liquefaction phenomena far from the epicenter. We proposed and evaluated the TDLI (temporal difference liquefaction index), which uses only one SWIR (short-wave infrared) band at 2200 nm, which is sensitive to soil moisture content. The Sentinel-2 TDLI was most consistent with field observations where sand blow from liquefaction was confirmed. We found that Sentinel-2, with its relatively shorter revisit period compared to that of Landsat 8 (5 days vs. 16 days), was more effective for detecting traces of short-lived liquefaction phenomena on the surface. The Sentinel-2 TDLI could help facilitate rapid investigations and responses to liquefaction damage.

scholarly journals Repeat optical satellite images reveal widespread and long term decrease in land-terminating glacier speeds

2012 ◽  
Vol 6 (2) ◽  
pp. 467-478 ◽  
Author(s):  
T. Heid ◽  
A. Kääb
Keyword(s):  
Mass Balance ◽  
Satellite Images ◽  
Average Rate ◽  
Glacier Mass Balance ◽  
Alaska Range ◽  
Ice Cap ◽  
Glacier Dynamics ◽  
The World ◽  
Speed Change ◽  
Optical Satellite Images

Abstract. By matching of repeat optical satellite images it is now possible to investigate glacier dynamics within large regions of the world and also between regions to improve knowledge about glacier dynamics in space and time. In this study we investigate whether the negative glacier mass balance seen over large parts of the world has caused the glaciers to change their speeds. The studied regions are Pamir, Caucasus, Penny Ice Cap, Alaska Range and Patagonia. In addition we derive speed changes for Karakoram, a region assumed to have positive mass balance and that contains many surge-type glaciers. We find that the mapped glaciers in the five regions with negative mass balance have over the last decades decreased their velocity at an average rate per decade of: 43 % in the Pamir, 8 % in the Caucasus, 25 % on Penny Ice Cap, 11 % in the Alaska Range and 20 % in Patagonia. Glaciers in Karakoram have generally increased their speeds, but surging glaciers and glaciers with flow instabilities are most prominent in this area. Therefore the calculated average speed change is not representative for this area.

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