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Special Issue "Remote Sensing of Glaciers"

A special issue of Remote Sensing (ISSN 2072-4292).

Deadline for manuscript submissions: closed (31 March 2017)

Special Issue Editors

Guest Editor
Dr. Frank Paul

Glaciology and Geomorphodynamics Group, Physical Geography Division, Department of Geography, University of Zurich, CH-8057 Zurich, Switzerland
Website | E-Mail
Interests: glacier mapping and monitoring from optical sensors; glacier response to climate change; geomorphometric DEM analysis; distributed mass balance modelling
Guest Editor
Dr. Kate Briggs

Centre for Polar Observation and Modelling (CPOM), School of Earth and Enviroment, University of Leeds, Leeds LS2 9JT, UK
Website | E-Mail
Interests: geodetic mass balance observations; altimetry, CryoSat-2; SAR velocity mapping
Guest Editor
Dr. Robert McNabb

Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, 0316 Oslo, Norway
Website | E-Mail
Interests: optical velocity mapping; glacier response and behavior; landsat
Guest Editor
Dr. Christopher Nuth

Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, 0316 Oslo, Norway
Website | E-Mail
Interests: geodetic mass balance; digital elevation model; glacier behavior and response; SFM
Guest Editor
Dr. Jan Wuite

ENVEO—Environmental Earth Observation IT, Technikerstraße 21a, A-6020, Innsbruck, Austria
Website | E-Mail
Interests: SAR ice velocity mapping glaciology; ice dynamics; satellite altimetry; mass balance studies

Special Issue Information

Dear Colleagues,

Studying glaciers from a wide range of remote sensing platforms and techniques has become an expanding field over the past decade. Key reasons for this are the now free availability of raw data (e.g. opening of the Landsat archive), the wide recognition of glaciers as indicators of climate change, and the strong impact of their changes on society at global (sea-level rise), to regional (run-off, hydro-power) and local (hazards) scales. In addition, the remoteness of glaciers, and difficulty to gain access to most of them for direct measurements, means that remote sensing data often provides the only viable means for studying them. Satellite data also measure parameters that are hard to obtain in the field and they complement ground-based observations in space and time. Hence, remote sensing of glaciers and their changes plays a fundamental role for our understanding of their characteristics, dynamics, future evolution and response to climate change.

Using optical and microwave imaging as well as altimetry sensors (such as Landsat, ASTER, Sentinel 1/2/3, SRTM, ALOS PALSAR, TerraSAR-X, ICESat, CryoSat 2), a wide range of glacier observations can be performed. Among the most common are mapping of glacier extents, and determination of elevation and volume changes, surface flow velocity, and snow lines. Several of them can be generated from the archived datasets over time periods of several decades, thus providing a robust means for change assessment and trend analysis. On the other hand, the ever-growing fleet of new satellites and sensors provide new possibilities for information extraction and accuracy improvement, but also require adaptation of existing algorithms to the new and advanced capabilities of the more recent sensors.

The Special Issue ‘Remote Sensing of Glaciers’ should provide a current overview on state-of-the-art methods for data retrieval from the diversity of sensors, as well as the latest applications of established methods to obtain new and quantitative information on glacier dynamics and changes over large regions. We focus on glaciers (and exclude the ice sheets of Greenland/Antarctica and their outlet glaciers and ice streams) to fully consider the specific challenges associated with remote sensing in steep, high-mountain topography. Potential topics include, but are not limited to:

  • Glacier and snow facies mapping and their changes through time
  • Derivation of glacier elevation and volume changes from DEMs and/or altimetry
  • Glacier surface velocities over large spatial regions and/or their trends over time
  • Fusion of sensors and methods to determine glaciological phenomena (e.g. debris cover)
  • Exploitation of new sensors (Sentinel 1A/1B and 2A, Landsat 8, PALSAR2, ...)
  • Novel methods for the generation of glacier extents, facies, elevation/elevation changes or velocity/velocity changes
  • Cross-comparison and integration of datasets derived from different sensors and platforms

Dr. Frank Paul
Dr. Kate Briggs
Dr. Robert McNabb
Dr. Christopher Nuth
Dr. Jan Wuite
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Remote Sensing is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Glacier extent and snow facies mapping
  • Glacier elevation and volume changes
  • Glacier flow velocities
  • Glacier changes and trend analysis
  • Combination and integration of methods and sensors
  • Optical and microwave imaging
  • Altimetry and DEM differencing
  • Sentinels

Published Papers (15 papers)

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Research

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Open AccessArticle Circum-Arctic Changes in the Flow of Glaciers and Ice Caps from Satellite SAR Data between the 1990s and 2017
Remote Sens. 2017, 9(9), 947; doi:10.3390/rs9090947
Received: 3 August 2017 / Revised: 28 August 2017 / Accepted: 8 September 2017 / Published: 12 September 2017
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Abstract
We computed circum-Arctic surface velocity maps of glaciers and ice caps over the Canadian Arctic, Svalbard and the Russian Arctic for at least two times between the 1990s and 2017 using satellite SAR data. Our analyses are mainly performed with offset-tracking of ALOS-1
[...] Read more.
We computed circum-Arctic surface velocity maps of glaciers and ice caps over the Canadian Arctic, Svalbard and the Russian Arctic for at least two times between the 1990s and 2017 using satellite SAR data. Our analyses are mainly performed with offset-tracking of ALOS-1 PALSAR-1 (2007–2011) and Sentinel-1 (2015–2017) data. In certain cases JERS-1 SAR (1994–1998), TerraSAR-X (2008–2012), Radarsat-2 (2009–2016) and ALOS-2 PALSAR-2 (2015–2016) data were used to fill-in spatial or temporal gaps. Validation of the latest Sentinel-1 results was accomplished by means of SAR data at higher spatial resolution (Radarsat-2 Wide Ultra Fine) and ground-based measurements. In general, we observe a deceleration of flow velocities for the major tidewater glaciers in the Canadian Arctic and an increase in frontal velocity along with a retreat of frontal positions over Svalbard and the Russian Arctic. However, all regions have strong accelerations for selected glaciers. The latter developments can be well traced based on the very high temporal sampling of Sentinel-1 acquisitions since 2015, revealing new insights in glacier dynamics. For example, surges on Spitsbergen (e.g., Negribreen, Nathorsbreen, Penckbreen and Strongbreen) have a different characteristic and timing than those over Eastern Austfonna and Edgeoya (e.g., Basin 3, Basin 2 and Stonebreen). Events similar to those ongoing on Eastern Austofonna were also observed over the Vavilov Ice Cap on Severnaya Zemlya and possibly Simony Glacier on Franz-Josef Land. Collectively, there seems to be a recently increasing number of glaciers with frontal destabilization over Eastern Svalbard and the Russian Arctic compared to the 1990s. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessFeature PaperEditor’s ChoiceArticle The 2015 Surge of Hispar Glacier in the Karakoram
Remote Sens. 2017, 9(9), 888; doi:10.3390/rs9090888
Received: 14 June 2017 / Revised: 4 August 2017 / Accepted: 15 August 2017 / Published: 26 August 2017
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Abstract
The Karakoram mountain range is well known for its numerous surge-type glaciers of which several have recently surged or are still doing so. Analysis of multi-temporal satellite images and digital elevation models have revealed impressive details about the related changes (e.g., in glacier
[...] Read more.
The Karakoram mountain range is well known for its numerous surge-type glaciers of which several have recently surged or are still doing so. Analysis of multi-temporal satellite images and digital elevation models have revealed impressive details about the related changes (e.g., in glacier length, surface elevation and flow velocities) and considerably expanded the database of known surge-type glaciers. One glacier that has so far only been reported as impacted by surging tributaries, rather than surging itself, is the 50 km long main trunk of Hispar Glacier in the Hunza catchment. We here present the evolution of flow velocities and surface features from its 2015/16 surge as revealed from a dense time series of SAR and optical images along with an analysis of historic satellite images. We observed maximum flow velocities of up to 14 m d−1 (5 km a−1) in spring 2015, sudden drops in summer velocities, a second increase in winter 2015/16 and a total advance of the surge front of about 6 km. During a few months the surge front velocity was much higher (about 90 m d−1) than the maximum flow velocity. We assume that one of its northern tributary glaciers, Yutmaru, initiated the surge at the end of summer 2014 and that the variability in flow velocities was driven by changes in the basal hydrologic regime (Alaska-type surge). We further provide evidence that Hispar Glacier has surged before (around 1960) over a distance of about 10 km so that it can also be regarded as a surge-type glacier. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Wavelet-Based Topographic Effect Compensation in Accurate Mountain Glacier Velocity Extraction: A Case Study of the Muztagh Ata Region, Eastern Pamir
Remote Sens. 2017, 9(7), 697; doi:10.3390/rs9070697
Received: 14 March 2017 / Revised: 26 June 2017 / Accepted: 2 July 2017 / Published: 6 July 2017
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Abstract
Glaciers in high mountain regions play an important role in global climate research. Glacier motion, which is the main characteristic of glacier activity, has attracted much interest and has been widely studied, because an accurate ice motion field is crucial for both glacier
[...] Read more.
Glaciers in high mountain regions play an important role in global climate research. Glacier motion, which is the main characteristic of glacier activity, has attracted much interest and has been widely studied, because an accurate ice motion field is crucial for both glacier activity analysis and ice avalanche prediction. Unfortunately, the serious topographic effects associated with the complex terrain in high mountain regions can result in errors in ice movement estimation. Thus, according to the different characteristics of the results of pixel tracking in the wavelet domain after random sample consensus (RANSAC)-based global deformation removal, a wavelet-based topographic effect compensation operation is presented in this paper. The proposed method is then used for ice motion estimation in the Muztagh Ata region, without the use of synthetic-aperture radar (SAR) imaging geometry parameters. The results show that the proposed method can effectively improve the accuracy of glacier motion estimation by reducing the mean and standard deviation values from 0.32 m and 0.4 m to 0.16 m and 0.23 m, respectively, in non-glacial regions, after precisely compensating the topographic effect with Advanced Land Observing Satellite–Phased Array-type L-band Synthetic Aperture Radar (ALOS–PALSAR) imagery. Therefore, the presented wavelet-based topographic effect compensation method is also effective without requiring the SAR imaging geometry parameters and has the potential to be widely used in the accurate estimation of mountain glacier velocity. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Seasonal and Interannual Variability of Columbia Glacier, Alaska (2011–2016): Ice Velocity, Mass Flux, Surface Elevation and Front Position
Remote Sens. 2017, 9(6), 635; doi:10.3390/rs9060635
Received: 27 March 2017 / Revised: 13 June 2017 / Accepted: 15 June 2017 / Published: 20 June 2017
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Abstract
Alaskan glaciers are among the largest contributors to sea-level rise outside the polar ice sheets. The contributions include dynamic discharge from marine-terminating glaciers which depends on the seasonally variable ice velocity. Columbia Glacier is a large marine-terminating glacier located in Southcentral Alaska that
[...] Read more.
Alaskan glaciers are among the largest contributors to sea-level rise outside the polar ice sheets. The contributions include dynamic discharge from marine-terminating glaciers which depends on the seasonally variable ice velocity. Columbia Glacier is a large marine-terminating glacier located in Southcentral Alaska that has been exhibiting pronounced retreat since the early 1980s. Since 2010, the glacier has split into two branches, the main branch and the west branch. We derived a 5-year record of surface velocity, mass flux (ice discharge), surface elevation and changes in front position using a dense time series of TanDEM-X synthetic aperture radar data (2011–2016). We observed distinct seasonal velocity patterns at both branches. At the main branch, the surface velocity peaked during late winter to midsummer but reached a minimum between late summer and fall. Its near-front velocity reached up to 14 m day−1 in May 2015 and was at its lowest speed of ~1 m day−1 in October 2012. Mass flux via the main branch was strongly controlled by the seasonal and interannual fluctuations of its velocity. The west branch also exhibited seasonal velocity variations with comparably lower magnitudes. The role of subglacial hydrology on the ice velocities of Columbia Glacier is already known from the published field measurements during summers of 1987. Our observed variability in its ice velocities on a seasonal basis also suggest that they are primarily controlled by the seasonal transition of the subglacial drainage system from an inefficient to an efficient and channelized drainage networks. However, abrupt velocity increase events for short periods (2014–2015 and 2015–2016 at the main branch, and 2013–2014 at the west branch) appear to be associated with strong near-front thinning and frontal retreat. This needs further investigation on the role of other potential controlling mechanisms. On the technological side, this study demonstrates the potential of high-resolution X-band SAR missions with a short revisit interval to examine glaciological variables and controlling processes. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Recent Deceleration of the Ice Elevation Change of Ecology Glacier (King George Island, Antarctica)
Remote Sens. 2017, 9(6), 520; doi:10.3390/rs9060520
Received: 2 March 2017 / Revised: 13 May 2017 / Accepted: 17 May 2017 / Published: 24 May 2017
Cited by 2 | PDF Full-text (7065 KB) | HTML Full-text | XML Full-text
Abstract
Glacier change studies in the Antarctic Peninsula region, despite their importance for global sea level rise, are commonly restricted to the investigation of frontal position changes. Here we present a long term (37 years; 1979–2016) study of ice elevation changes of the Ecology
[...] Read more.
Glacier change studies in the Antarctic Peninsula region, despite their importance for global sea level rise, are commonly restricted to the investigation of frontal position changes. Here we present a long term (37 years; 1979–2016) study of ice elevation changes of the Ecology Glacier, King George Island ( 62 11 S, 58 29 W). The glacier covers an area of 5.21 km 2 and is located close to the H. Arctowski Polish Antarctic Station, and therefore has been an object of various multidisciplinary studies with subject ranging from glaciology, meteorology to glacial microbiology. Hence, it is of great interest to assess its current state and put it in a broader context of recent glacial change. In order to achieve that goal, we conducted an analysis of archival cartographic material and combined it with field measurements of proglacial lagoon hydrography and state-of-art geodetic surveying of the glacier surface with terrestrial laser scanning and satellite imagery. Overall mass loss was largest in the beginning of 2000s, and the rate of elevation change substantially decreased between 2012–2016, with little ice front retreat and no significant surface lowering. Ice elevation change rate for the common ablation area over all analyzed periods (1979–2001–2012–2016) has decreased from −1.7 ± 0.4 m/year in 1979–2001 and −1.5 ± 0.5 m/year in 2001–2012 to −0.5 ± 0.6 m/year in 2012–2016. This reduction of ice mass loss is likely related to decreasing summer temperatures in this region of the Antarctic Peninsula. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Glacier Changes in the Susitna Basin, Alaska, USA, (1951–2015) using GIS and Remote Sensing Methods
Remote Sens. 2017, 9(5), 478; doi:10.3390/rs9050478
Received: 18 March 2017 / Revised: 1 May 2017 / Accepted: 5 May 2017 / Published: 14 May 2017
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Abstract
The Susitna River draining from the highly glacierized Central Alaska Range has repeatedly been considered a potential hydro-power source in recent decades, raising questions about the effect of glacier changes on the basin’s river runoff. We determine changes in the glacier area (1951–2010),
[...] Read more.
The Susitna River draining from the highly glacierized Central Alaska Range has repeatedly been considered a potential hydro-power source in recent decades, raising questions about the effect of glacier changes on the basin’s river runoff. We determine changes in the glacier area (1951–2010), elevation (1951–2010, 1951–2005 and 2005–2010), equilibrium line altitude (ELA, 1999–2015), and accumulation area ratio (AAR, 1999–2015) of the basin’s five largest glaciers covering 587 km² (2010). We use the Landsat time series, as well as digital elevation models (DEMs) from 1951 (United States Geological Survey (USGS) aerial imagery), 2005 (Advanced Spaceborne Thermal Emission and Reflection Radiometer, ASTER), and 2010 (airborne interferometric synthetic aperture radar, IfSAR). The glaciers lost an area of 128 ± 15 km² (16%) between 1951 and 2010. The mean ELA was located at 1745 ± 88 m a.s.l. during 1999–2015. The glacier’s annual ELAs do not show any significant trends. We found a glacier-wide elevation change of −0.41 ± 0.07 m yr−1 for the period 1951–2005 and −1.20 ± 0.25 m yr−1 for 2005–2010. The results indicate that the glaciers are in a state of retreat and thinning, and have been losing mass at an accelerated rate in recent years. The interpretation of the thickness changes is complicated by the glaciers’ surge cycles. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Glacier Surface Velocity Retrieval Using D-InSAR and Offset Tracking Techniques Applied to Ascending and Descending Passes of Sentinel-1 Data for Southern Ellesmere Ice Caps, Canadian Arctic
Remote Sens. 2017, 9(5), 442; doi:10.3390/rs9050442
Received: 31 January 2017 / Revised: 28 April 2017 / Accepted: 1 May 2017 / Published: 5 May 2017
Cited by 1 | PDF Full-text (6202 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The Terrain Observation by Progressive Scans (TOPS) acquisition mode of the Sentinel-1 mission provides a wide coverage per acquisition with resolutions of 5 m in range and 20 m in azimuth, which makes this acquisition mode attractive for glacier velocity monitoring. Here, we
[...] Read more.
The Terrain Observation by Progressive Scans (TOPS) acquisition mode of the Sentinel-1 mission provides a wide coverage per acquisition with resolutions of 5 m in range and 20 m in azimuth, which makes this acquisition mode attractive for glacier velocity monitoring. Here, we retrieve surface velocities from the southern Ellesmere Island ice caps (Canadian Arctic) using both offset tracking and Differential Interferometric Synthetic Aperture Radar (D-InSAR) techniques and combining ascending and descending passes. We optimise the offset tracking technique by omitting the azimuth offsets. By doing so, we are able to improve the final resolution of the velocity product, as Sentinel-1 shows a lower resolution in the azimuth direction. Simultaneously, we avoid the undesired ionospheric effect manifested in the data as azimuth streaks. The D-InSAR technique shows its merits when applied to slow-moving areas, while offset tracking is more suitable for fast-moving areas. This research shows that the methods used here are complementary and the use of both to determine glacier velocities is better than only using one or the other. We observe glacier surface velocities of up to 1200 m year 1 for the fastest tidewater glaciers. The land-terminating glaciers show typical velocities between 12 and 33 m year 1 , though with peaks up to 150 m year 1 in narrowing zones of the confining valleys. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Evaluation of MODIS Albedo Product over Ice Caps in Iceland and Impact of Volcanic Eruptions on Their Albedo
Remote Sens. 2017, 9(5), 399; doi:10.3390/rs9050399
Received: 17 February 2017 / Revised: 31 March 2017 / Accepted: 13 April 2017 / Published: 25 April 2017
Cited by 1 | PDF Full-text (4975 KB) | HTML Full-text | XML Full-text
Abstract
Albedo is a key variable in the response of glaciers to climate. In Iceland, large albedo variations of the ice caps may be caused by the deposition of volcanic ash (tephra). Sparse in situ measurements are insufficient to characterize the spatial variation of
[...] Read more.
Albedo is a key variable in the response of glaciers to climate. In Iceland, large albedo variations of the ice caps may be caused by the deposition of volcanic ash (tephra). Sparse in situ measurements are insufficient to characterize the spatial variation of albedo over the ice caps due to their large size. Here we evaluated the latest MCD43 MODIS albedo product (collection 6) to monitor albedo changes over the Icelandic ice caps using albedo measurements from ten automatic weather stations on Vatnajökull and Langjökull. Furthermore, we examined the influence of the albedo variability within MODIS pixels by comparing the results with a collection of Landsat scenes. The results indicate a good ability of the MODIS product to characterize the seasonal and interannual albedo changes with correlation coefficients ranging from 0.47 to 0.90 (median 0.84) and small biases ranging from −0.07 to 0.09. The root-mean square errors (RMSE) ranging from 0.08 to 0.21, are larger than that from previous studies, but we did not discard the retrievals flagged as bad quality to maximize the amount of observations given the frequent cloud obstruction in Iceland. We found a positive but non-significant relationship between the RMSE and the subpixel variability as indicated by the standard deviation of the Landsat albedo within a MODIS pixel (R = 0.48). The summer albedo maps and time series computed from the MODIS product show that the albedo decreased significantly after the 2010 Eyjafjallajökull and 2011 Grímsvötn eruptions on all the main ice caps except the northernmost Drangajökull. A strong reduction of the summer albedo by up to 0.6 is observed over large regions of the accumulation areas. These data can be assimilated in an energy and mass balance model to better understand the relative influence of the volcanic and climate forcing to the ongoing mass losses of Icelandic ice caps. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle A Glacier Surge of Bivachny Glacier, Pamir Mountains, Observed by a Time Series of High-Resolution Digital Elevation Models and Glacier Velocities
Remote Sens. 2017, 9(4), 388; doi:10.3390/rs9040388
Received: 31 January 2017 / Revised: 31 March 2017 / Accepted: 9 April 2017 / Published: 20 April 2017
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Abstract
Surge-type glaciers are characterised by relatively short phases of enhanced ice transport and mass redistribution after a comparatively long quiescent phase when the glacier is virtually inactive. This unstable behaviour makes it difficult to assess the influence of climate change on those glaciers.
[...] Read more.
Surge-type glaciers are characterised by relatively short phases of enhanced ice transport and mass redistribution after a comparatively long quiescent phase when the glacier is virtually inactive. This unstable behaviour makes it difficult to assess the influence of climate change on those glaciers. We describe the evolution of the most recent surge of Bivachny Glacier in the Pamir Mountains, Tajikistan between 2011 and 2015 with respect to changes in its topography and dynamics. For the relevant time span, nine digital elevation models were derived from TanDEM-X data; optical satellite data (Landsat 5, 7 and 8, EO-1) as well as synthetic aperture radar data (TerraSAR-X and TanDEM-X) were used to analyse ice flow velocities. The comparison of the topography at the beginning of the surge with the one observed by the Shuttle Radar Topography Mission in 2000 revealed a thickening in the upper part of the ablation area of the glacier and a thinning further down the glacier as is typically observed during the quiescent phase. During the active phase, a surge bulge measuring up to around 80 m developed and travelled downstream for a distance of 13 km with a mean velocity of 4400 m year−1. Ice flow velocities increased from below 90 m year−1 duringthe quiescent phase in 2000 to up to 3400 m year−1 in spring 2014. After reaching the confluence with Fedchenko Glacier, the surge slowed down until it completely terminated in 2015. The observed seasonality of the glacier velocities with a regular speed-up during the onset of the melt period suggests a hydrological control of the surge related to the effectiveness of the subglacial drainage system. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessFeature PaperArticle Elevation Change and Improved Velocity Retrieval Using Orthorectified Optical Satellite Data from Different Orbits
Remote Sens. 2017, 9(3), 300; doi:10.3390/rs9030300
Received: 21 January 2017 / Revised: 15 March 2017 / Accepted: 17 March 2017 / Published: 22 March 2017
Cited by 6 | PDF Full-text (22860 KB) | HTML Full-text | XML Full-text
Abstract
Optical satellite products are available at different processing levels. Of these products, terrain corrected (i.e., orthorectified) products are the ones mostly used for glacier displacement estimation. For terrain correction, a digital elevation model (DEM) is used that typically stems from various data sources
[...] Read more.
Optical satellite products are available at different processing levels. Of these products, terrain corrected (i.e., orthorectified) products are the ones mostly used for glacier displacement estimation. For terrain correction, a digital elevation model (DEM) is used that typically stems from various data sources with variable qualities, from dispersed time instances, or with different spatial resolutions. Consequently, terrain representation used for orthorectifying satellite images is often in disagreement with reality at image acquisition. Normally, the lateral orthoprojection offsets resulting from vertical DEM errors are taken into account in the geolocation error budget of the corrected images, or may even be neglected. The largest offsets of this type are often found over glaciers, as these may show strong elevation changes over time and thus large elevation errors in the reference DEM with respect to image acquisition. The detection and correction of such orthorectification offsets is further complicated by ice flow which adds a second offset component to the displacement vectors between orthorectified data. Vice versa, measurement of glacier flow is complicated by the inherent superposition of ice movement vectors and orthorectification offset vectors. In this study, we try to estimate these orthorectification offsets in the presence of terrain movement and translate them to elevation biases in the reference surface. We demonstrate our method using three different sites which include very dynamic glaciers. For the Oriental Glacier, an outlet of the Southern Patagonian icefield, Landsat 7 and 8 data from different orbits enabled the identification of trends related to elevation change. For the Aletsch Glacier, Swiss Alps, we assess the terrain offsets of both Landsat 8 and Sentinel-2A: a superior DEM appears to be used for Landsat in comparison to Sentinel-2, however a systematic bias is observed in the snow covered areas. Lastly, we demonstrate our methodology in a pipeline structure; displacement estimates for the Helheim-glacier, in Greenland, are mapped and corrected for orthorectification offsets between data from different orbits, which enables a twice as dense a temporal resolution of velocity data, as compared to the standard method of measuring velocities from repeat-orbit data only. In addition, we introduce and implement a novel matching method which uses image triplets. By formulating the three image displacements as a convolution, a geometric constraint can be exploited. Such a constraint enhances the reliability of the displacement estimations. Furthermore the implementation is simple and computationally swift. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Glacier Mass Loss during the 1960s and 1970s in the Ak-Shirak Range (Kyrgyzstan) from Multiple Stereoscopic Corona and Hexagon Imagery
Remote Sens. 2017, 9(3), 275; doi:10.3390/rs9030275
Received: 2 December 2016 / Revised: 7 March 2017 / Accepted: 12 March 2017 / Published: 16 March 2017
PDF Full-text (13131 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Comprehensive research on glacier changes in the Tian Shan is available for the current decade; however, there is limited information about glacier investigations of previous decades and especially before the mid 1970s. The earliest stereo images from the Corona missions were acquired in
[...] Read more.
Comprehensive research on glacier changes in the Tian Shan is available for the current decade; however, there is limited information about glacier investigations of previous decades and especially before the mid 1970s. The earliest stereo images from the Corona missions were acquired in the 1960s but existing studies dealing with these images focus on single glaciers or small areas only. We developed a workflow to generate digital terrain models (DTMs) and orthophotos from 1964 Corona KH-4 for an entire mountain range (Ak-Shirak) located in the Central Tian Shan. From these DTMs and orthoimages, we calculated geodetic mass balances and length changes in comparison to 1973 and 1980 Hexagon KH-9 data. We found mass budgets between −0.4 ± 0.1 m·w.e.a−1 (1964–1980) and −0.9 ± 0.4 m·w.e.a−1 (1973–1980) for the whole region and individual glaciers. The length changes, on the other hand, vary heterogeneously between +624 ± 18 m (+39.0 ± 1.1 m·a−1) and −923 ± 18 m (−57.7 ± 1.1 m·a−1) for 1964–1980. An automation of the processing line can successively lead to region-wide Corona data processing allowing the analysis and interpretation of glacier changes on a larger scale and supporting a refinement of glacier modelling. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Reflectance–Elevation Relationships and Their Seasonal Patterns over Twelve Glaciers in Western China Based on Landsat 8 Data
Remote Sens. 2017, 9(3), 187; doi:10.3390/rs9030187
Received: 15 December 2016 / Revised: 13 February 2017 / Accepted: 20 February 2017 / Published: 23 February 2017
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Abstract
Albedo/reflectance is of great importance for glaciers’ mass balance and energy budget. Elevation could be a major factor of influence for glacier reflectance, and therefore when studying glacier reflectance, the altitude ranges should be considered. However, due to the limitations of traditional earth
[...] Read more.
Albedo/reflectance is of great importance for glaciers’ mass balance and energy budget. Elevation could be a major factor of influence for glacier reflectance, and therefore when studying glacier reflectance, the altitude ranges should be considered. However, due to the limitations of traditional earth observation systems, conventional analyses usually consider the spatial and temporal patterns of the reflectance average, which is severely restricted. The launch of Landsat-8 gives us the opportunity to study the seasonal glacier reflectance–elevation relationship. We have obtained the monthly near-nadir reflectance per 100 m for twelve glaciers in western China based on 372 scenes of Landsat 8 images acquired from April 2013 to December 2015. Variations of monthly broadband reflectance, reflectance–elevation relationships and reflectance gradients are analyzed and discussed. The results show that the linear trend of the reflectance–elevation relationship (when the altitude is less than 6100 m) is very significant; elevation has greater influence than location on seasonal reflectance variations; and the level of glacier reflectance gradient may relate with its climate. This may be the first work that has used remote-sensing data to analyze seasonal glacier reflectance–elevation patterns. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle Cross-Comparison of Albedo Products for Glacier Surfaces Derived from Airborne and Satellite (Sentinel-2 and Landsat 8) Optical Data
Remote Sens. 2017, 9(2), 110; doi:10.3390/rs9020110
Received: 21 October 2016 / Accepted: 19 January 2017 / Published: 27 January 2017
Cited by 2 | PDF Full-text (13297 KB) | HTML Full-text | XML Full-text
Abstract
Surface albedo partitions the amount of energy received by glacier surfaces from shortwave fluxes and modulates the energy available for melt processes. The ice-albedo feedback, influenced by the contamination of bare-ice surfaces with light-absorbing impurities, plays a major role in the melting of
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Surface albedo partitions the amount of energy received by glacier surfaces from shortwave fluxes and modulates the energy available for melt processes. The ice-albedo feedback, influenced by the contamination of bare-ice surfaces with light-absorbing impurities, plays a major role in the melting of mountain glaciers in a warming climate. However, little is known about the spatial and temporal distribution and variability of bare-ice glacier surface albedo under changing conditions. In this study, we focus on two mountain glaciers located in the western Swiss Alps and perform a cross-comparison of different albedo products. We take advantage of high spectral and spatial resolution (284 bands, 2 m) imaging spectrometer data from the Airborne Prism Experiment (APEX) and investigate the applicability and potential of Sentinel-2 and Landsat 8 data to derive broadband albedo products. The performance of shortwave broadband albedo retrievals is tested and we assess the reliability of published narrow-to-broadband conversion algorithms. The resulting albedo products from the three sensors and different algorithms are further cross-compared. Moreover, the impact of the anisotropy correction is analysed depending on different surface types. While degradation of the spectral resolution impacted glacier-wide mean albedo by about 5%, reducing the spatial resolution resulted in changes of less than 1%. However, in any case, coarser spatial resolution was no longer able to represent small-scale variability of albedo on glacier surfaces. We discuss the implications when using Sentinel-2 and Landsat 8 to map dynamic glaciological processes and to monitor glacier surface albedo on larger spatial and more frequent temporal scales. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Open AccessArticle An Inter-Comparison of Techniques for Determining Velocities of Maritime Arctic Glaciers, Svalbard, Using Radarsat-2 Wide Fine Mode Data
Remote Sens. 2016, 8(9), 785; doi:10.3390/rs8090785
Received: 20 July 2016 / Revised: 12 September 2016 / Accepted: 16 September 2016 / Published: 21 September 2016
Cited by 4 | PDF Full-text (29991 KB) | HTML Full-text | XML Full-text
Abstract
Glacier dynamics play an important role in the mass balance of many glaciers, ice caps and ice sheets. In this study we exploit Radarsat-2 (RS-2) Wide Fine (WF) data to determine the surface speed of Svalbard glaciers in the winters of 2012/2013 and
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Glacier dynamics play an important role in the mass balance of many glaciers, ice caps and ice sheets. In this study we exploit Radarsat-2 (RS-2) Wide Fine (WF) data to determine the surface speed of Svalbard glaciers in the winters of 2012/2013 and 2013/2014 using Synthetic Aperture RADAR (SAR) offset and speckle tracking. The RS-2 WF mode combines the advantages of the large spatial coverage of the Wide mode (150 × 150 km) and the high pixel resolution (9 m) of the Fine mode and thus has a major potential for glacier velocity monitoring from space through offset and speckle tracking. Faster flowing glaciers (1.95 m·d−1–2.55 m·d−1) that are studied in detail are Nathorstbreen, Kronebreen, Kongsbreen and Monacobreen. Using our Radarsat-2 WF dataset, we compare the performance of two SAR tracking algorithms, namely the GAMMA Remote Sensing Software and a custom written MATLAB script (GRAY method) that has primarily been used in the Canadian Arctic. Both algorithms provide comparable results, especially for the faster flowing glaciers and the termini of slower tidewater glaciers. A comparison of the WF data to RS-2 Ultrafine and Wide mode data reveals the superiority of RS-2 WF data over the Wide mode data. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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Review

Jump to: Research

Open AccessReview Annual and Seasonal Glacier-Wide Surface Mass Balance Quantified from Changes in Glacier Surface State: A Review on Existing Methods Using Optical Satellite Imagery
Remote Sens. 2017, 9(5), 507; doi:10.3390/rs9050507
Received: 23 February 2017 / Revised: 11 May 2017 / Accepted: 16 May 2017 / Published: 20 May 2017
PDF Full-text (5933 KB) | HTML Full-text | XML Full-text
Abstract
Glaciers are one of the terrestrial essential climate variables (ECVs) as they respond very sensitively to climate change. A key driver of their response is the glacier surface mass balance that is typically derived from field measurements. It deserves to be quantified over
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Glaciers are one of the terrestrial essential climate variables (ECVs) as they respond very sensitively to climate change. A key driver of their response is the glacier surface mass balance that is typically derived from field measurements. It deserves to be quantified over long time scales to better understand the accumulation and ablation processes at the glacier surface and their relationships with inter-annual changes in meteorological conditions and long-term climate changes. Glaciers with in situ monitoring of surface mass balance are scarce at the global scale, and satellite remote sensing provides a powerful tool to increase the number of monitored glaciers. In this study, we present a review of three optical remote sensing methods developed to quantify seasonal and annual glacier surface mass balances. These methodologies rely on the multitemporal monitoring of the end-of-summer snow line for the equilibrium-line altitude (ELA) method, the annual cycle of glacier surface albedo for the albedo method and the mapping of the regional snow cover at the seasonal scale for the snow-map method. Together with a presentation of each method, an application is illustrated. The ELA method shows promising results to quantify annual surface mass balance and to reconstruct multi-decadal time series. The other two methods currently need a calibration on the basis of existing in situ data; however, a generalization of these methods (without calibration) could be achieved. The two latter methods show satisfying results at the annual and seasonal scales, particularly for the summer surface mass balance in the case of the albedo method and for the winter surface mass balance in the case of the snow-map method. The limits of each method (e.g., cloud coverage, debris-covered glaciers, monsoon-regime and cold glaciers), their complementarities and the future challenges (e.g., automating of the satellite images processing, generalization of the methods needing calibration) are also discussed. Full article
(This article belongs to the Special Issue Remote Sensing of Glaciers)
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