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Landsat 8 image (bands 6, 5 and 4 combined) of Walsh Glacier on 11 August 2013, superimposed with the Glacier boundary and manually delineated centerline. The white dots mark 10 km intervals from the terminus.
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Many surge-type glaciers are present on the St. Elias Mountains, but a detailed study on the surge behavior of the glaciers is still missing. In this study, we used remote sensing data to reveal detailed glacier surge behavior, focusing on the recent surge at Walsh Glacier, which was reported to have surged once in the 1960s. Glacial velocities wer...
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... Glacier is located in the St. Elias Mountains (Figure 1), which straddle the border between Alaska, Yukon, and British Columbia. With a glaciated area of 33,170 km 2 , the St. Elias Mountains make up one of the largest extra-polar ice masses in the world [24]. ...
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... can be seen that, before winter 2014, the velocity below 50 km from the terminus remained very low. From winter 2014, the velocity accelerated at 50-60 km from the terminus, which was almost where the conjunction of the eastern branch and northern branch was situated, as seen from Figure 1. The surge then rapidly spread downward. ...
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... The surge behaviors of Chitina Glacier, Walsh Glacier and Logan Glacier show distinct differences in the impact on the elevation change of sites, distributed near the termini of the glaciers. Specifically, numerous surge records of the Chitina Glacier and Walsh Glacier during our study period revealed that the surge front was far away from the glacier terminus (the nearest distance was about 20 km) (Abe & Furuya, 2015;Fu & Zhou, 2020;Waechter et al., 2015). The mass redistribution caused by the surges didn't affect the monotonic decrease in the elevation of Sites 3 and 4 ( Figure 14). ...
Radar altimetry has been used to monitor sea level changes and ice sheet elevation changes for decades. Over mountain glaciers, radar altimetry has limited applications due to contaminated waveforms caused by complex glacier surfaces and steep terrains. In this study, we develop a glacier‐threshold method (GTM) to determine glacier elevation changes in Alaska and Yukon. The GTM retracks waveforms, reduces terrain effect and detects invalid elevation observations from the TOPEX/Poseidon (T/P) and Jason‐2 (J2) altimeters, resulting in an average usable rate of 35% from original altimeter‐measured heights. The selected measurements are used to construct time series of glacier elevation changes over 1993–2002 (T/P) and 2008–2016 (J2) at 47 sites. A crossover analysis, validation by airborne laser altimetry observations, and comparisons with recent studies confirm the estimated glacier elevation changes. Our findings suggest that the thinning of glaciers in Alaska and Yukon has been ubiquitous in recent years. The site near Walsh Glacier has the highest thinning rate of −5.71 ± 0.09 m/yr, followed by Chitina Glacier at −4.51 ± 0.21 m/yr. Only 17% of sites show glacier thickening due to surges and mass accumulations. Using a sophisticated data processing algorithm like the GTM, we show that altimeter data from the repeat TOPEX‐Jason missions can be used to monitor long‐term glacier elevation changes at inaccessible spots, creating an additional value for altimeter missions originally purposed for monitoring long‐term sea level change.
... When the meltwater discharges high in the summer, the lakes are generally empty (Marston 2011). Glacier surge also results in the total transformation of the normal glacier surface into a heavily crevassed one due to the stress induced by the glacier side walls (Fu and Zhou 2020). Sometimes this can lead to very rapid advances in the glacier front. ...
Glaciers in the Karakoram region are widely recognized for their historical surging phenomenon. Accurate field-based glacier monitoring is challenging in the Karakoram due to the presence of mixed-nature glaciers that are advancing, receding , and surging. Many geographers came to the opinion that surging is a thermally controlled activity in the Karakoram as opposed to a hydrologically controlled activity as a result of characteristics including high-altitude warmth, precipitation, and accumulation patterns of these glaciers. But the main surge mechanism is still a mystery. The current study used Landsat multispectral satellite datasets to examine and investigate the glaciers' vulnerability to surging activity in the Hunza basin based on the annual surface ice flow rate and frontal snout advancement of the glaciers from 1990 to 2021. Around 80 glaciers in the Hunza basin have been researched, and based on interannual surface flow rates, it has been determined that Batura, Hassanabad II, Barpu, Gharesa, Hispar, Khurdopin, Minapin, Virjerab, Yazgil, and Ghulkin glaciers are more vulnerable to surging. The findings show that during the research period, these glaciers had surged and advanced along their snouts. The frontal snout of these glaciers advances, and moraines are deposited closer to the glacier terminus as a consequence of active surge points over the ablation region. The Hunza basin's topography, precipitation, and thermal regimes regulate the glaciers' surging phenomena causing successive acceleration in the glaciers. Field-based measurements made with a differential global positioning system are used to corroborate the obtained results.
... They conclude the precipitation and slope set up a primary control over the surging glaciers. Thus, to investigate a glacier advancement, the glacier's climatic and topographic attributes need to be linked with the earlier findings on other factors of the glacier surge (Fu and Zhou 2020). However, the annual and seasonal glaciological data is often scarce, which is the foremost hurdle to study the mass balance change and surges (Pfeffer et al. 2014;Quincey et al. 2015;Ashraf et al. 2017). ...
Karakorum glaciers are well known for the advancement and the formation of new glacial lakes due to accelerated climate warming. Its Shimshal valley is profoundly affected by glacier surges in the last couple of decades. Khurdopin glacier is one of the highly surging glaciers in the Karakorum region. Its continuous surge since the nineteenth century is blocking the Shimshal River and creating new lakes. Our objective is to investigate the Khurdopin glacier surge from 1999 to 2017. With this, we aim to identify possible climate and topographic controls on the glacier surge behaviour. We used Landsat 4–5, 7 and 8 satellite bands and ground observations to estimate the glacier retreat and new land cover types from the glacier surge. Our results show that the Khurdopin glacier surges every 20 years. We observed the first surge of 0.69 Km2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^2$$\end{document} in 2000 and the second surge of 0.63 Km2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^2$$\end{document} in 2017. Both events blocked the Shimshal River. We observed an increase of 1–4 °C in the glacier minimum and maximum winter temperatures. Moreover, we observed snowfall variations in the accumulation zone in the steep glacier slope with a north slope-aspect. The 64% of the glacier aspect is north that causes an increase in ice mass in the accumulation zone by receiving more snowfall in the winter season. The study output, combined with earlier findings, can further predict a surge event in the future.
... Our records capture the last year of surge activity along this glacier. Our records also show the last six months of surge activity along the Walsh Glacier (P11) that was initiated before 2015 (Fu and Zhou 2020). These results demonstrate how the use of ascending and descending data to create a dense observational record can be used to evaluate the horizontal and vertical flow variations related to ice dynamics on surge-type glaciers (e.g. ...
Modern remote sensing techniques, such as Synthetic Aperture Radar (SAR), can measure the direction and intensity of glacier flow. Yet the question remains as to what these measurements reveal about glaciers' adjustment to the warming climate. Here, we present a technique that addresses this question by linking the SAR-derived velocity measurements with the glacier elevation change and the specific mass balance (i.e. mass balance per unit area). The technique computes the speckle offset tracking results from the north, east and vertical flow displacement time series, with the vertical component further split into a Surface Parallel Flow (SPF) advection component due to the motion along a glacier surface slope and a non-Surface Parallel Flow (nSPF). The latter links the glacier surface elevation change with the specific mass balance and strain rates. We apply this technique to ascending and descending Sentinel-1 data to derive the four-dimensional flow displacement time series for glaciers in southeast Alaska during 2016–2019. Time series extracted for a few characteristic regions demonstrate remarkable temporal variability in flow velocities. The seasonal signal observed in the nSPF component is modeled using the Positive Degree Day model. This method can be used for computing either mass balance or glacier surface elevation change if one of these two parameters is known from external observations.
Climate change has reduced global ice mass over the last 2 decades as enhanced warming has accelerated surface melt and runoff rates. Glaciers have undergone dynamic processes in response to a warming climate that impacts the surface geometry and mass distribution of glacial ice. Until recently no single technique could consistently measure the evolution of surface flow for an entire glaciated region in three dimensions with high temporal and spatial resolution. We have improved upon earlier methods by developing a technique for mapping, in unprecedented detail, the temporal evolution of glaciers. Our software computes north, east, and vertical flow velocity and/or displacement time series from the synthetic aperture radar (SAR) ascending and descending range and azimuth speckle offsets. The software can handle large volumes of satellite data and is designed to work on high-performance computers (HPCs) as well as workstations by utilizing multiple parallelization methods. We then compute flow velocity–displacement time series for glaciers in southeastern Alaska during 2016–2021 and observe seasonal and interannual variations in flow velocities at Seward and Malaspina glaciers as well as culminating phases of surging at Klutlan, Walsh, and Kluane glaciers. On a broader scale, this technique can be used for reconstructing the response of worldwide glaciers to the warming climate using archived SAR data and for near-real-time monitoring of these glaciers using rapid revisit SAR data from satellites, such as Sentinel-1 (6 or 12 d revisit period) and the forthcoming NISAR mission (12 d revisit period).
The detailed study of glacier surges in St. Elias Mountains is very scarce.Robust and repeat observation of surface displacement, elevation changes and surge reoccurrence intervalsare limited to few surge-type glaciers (e.g., Variegated, Bearing, Lowell and Donjek). Therefore, this study presents the first detailed surge dynamics of Klutlan (1990-2019) and Fisher (1984-2019) glaciers in the St. Elias Mountains, North America. Surface displacement estimation using optical imagery (Landsat TM, ETM+, OLI and Sentinel 2) and surface elevation changes derived from ASTER DEMs were used to understand the surge dynamics. Klutlan Glacier lackspre-surge acceleration and had six years longactive phase (2013-2019). The surge of Klutlan Glacier showed two surface flow maxima(6.2 ± 0.2 m d ⁻¹ and ~5 ± 0.2 m d ⁻¹ ),in summer of 2016 and2018 respectively.During 2019-2020, in the reservoir zone, maximum surface lowering of -65± 33m was observed whereas, in the receiving zone, maximum ice thickness increased by +31 ± 40 m. The dynamic balance line (DBL)on Klutlan Glaciermoved ~16 km down-glacier during 2019 (788masl.) in comparison with 2004 (1998 masl.). The Fisher Glacier exhibitssix years (2007-2013) long pre-surge acceleration, three years (2013-2016) long active phase and surge terminated gradually. The peak surge displacement ~7 ± 0.4 m d ⁻¹ was observed in summer of 2015. The reservoir zone experienced a maximum lowering of -60 ± 22 mfrom 2019 to 2003 while lower receiving zone maximum thickened by +80± 22 m. The DBL shifted ~3 km down-glacier during 2019 (959 masl.) as compared to 2016 (1006 masl.). This study assumes that the surge of Fisher Glacier is partially matched with a thermally controlled surge. However, the surge characteristics of Klutlan Glacier doesnot corroborate with globally recognised hydrological or thermally controlled surge mechanism.
