valley glacier
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2021 ◽  
Author(s):  
Marc Hugentobler ◽  
Jordan Balfour Aaron ◽  
Simon Loew ◽  
Clement Roques
Keyword(s):  

2021 ◽  
Vol 21 (9) ◽  
pp. 2791-2810
Author(s):  
Xiaowen Wang ◽  
Lin Liu ◽  
Yan Hu ◽  
Tonghua Wu ◽  
Lin Zhao ◽  
...  

Abstract. Detachments of large parts of low-angle mountain glaciers in recent years have raised great attention due to their threats to lives and properties downstream. While current studies have mainly focused on post-event analysis, a few opportunities have presented themselves to assess the potential hazards of a glacier prone to detachment. Here we present a comprehensive analysis of the dynamics and runout hazard of a low-angle (∼20∘) valley glacier, close to the Qinghai–Tibet railway and highway, in the East Kunlun Mountains on the Qinghai–Tibet Plateau. The changes in morphology, terminus position, and surface elevation of the glacier between 1975 and 2021 were characterized with a stereo-image pair from the historical KH-9 spy satellite, six digital elevation models (DEMs), and 11 high-resolution images from Planet Labs. The surface flow velocities of the glacier tongue between 2009 and 2020 were also tracked based on cross-correlation of Planet images. Our observations show that the glacier snout has been progressively advancing in the past 4 decades, with a stepwise increase in advance velocity from 4.55±0.46ma-1 between 1975 and 2009 to 30.88±2.36ma-1 between 2015 and 2020. DEM differencing confirms the glacial advance, with surface thinning in the source region and thickening in the tongue. The net volume loss over the glacier tongue was about 11.21±2.66×105 m3 during 1975–2018. Image cross-correlation reveals that the surface flow velocity of the glacier tongue has been increasing in recent years, with the mean velocity below 4800 m more than tripling from 6.3±1.8ma-1 during 2009–2010 to 22.3±3.2ma-1 during 2019–2020. With a combined analysis of the geomorphic, climatic, and hydrologic conditions of the glacier, we suggest that the flow of the glacier tongue is mainly controlled by the glacier geometry, while the presence of an ice-dammed lake and a supraglacial pond implies a hydrological influence as well. Taking the whole glacier and glacier tongue as two endmember avalanche sources, we assessed the potential runout distances of these two scenarios using the angle of reach and the Voellmy–Salm avalanche model. The assessments show that the avalanche of the whole glacier would easily travel a distance that would threaten the safety of the railway. In contrast, the detachment of the glacier tongue would threaten the railway only with a small angle of reach or when employing a low-friction parameter in the Voellmy–Salm modeling.


2021 ◽  
Author(s):  
Rossana Serandrei-Barbero ◽  
Sandra Donnici ◽  
Stefano Zecchetto

Abstract. The behaviour of the valley glaciers of the Italian Alps as a result of the climate changes expected for the 21st century has been investigated. From 1980 to 2017 the average length reductions of these glaciers has been 16 % and their average areal reduction around 22 %, much smaller than the overall glacier retreat of the Alps. Their mean observed shortening was about 500 m for a temperature increase of 1.4 °C. To quantify the valley glacier life expectancy, a model estimating their length variations from the air temperature variations of the EuroCordex climatological projections of six different models under RCP4.5 and RCP8.5 scenarios has been used. The ensemble mean temperatures in the Italian Alps region under these scenarios indicate increases of temperature of ~2 °C and ~4 °C from 2018 to 2100 respectively. In both scenarios, the glacier model projections show a constant retreat until the eighties, weakening towards the end of the century. As expected, it resulted more severe under the RCP8.5 (from 22 % to 48 %) than under the RCP4.5 (from 10 % to 25 %) scenario, with a mean length shortening of 35 % and 13 % respectively by 2100. The model used estimates that the majority of the valley glaciers could better resist the climate change.


2021 ◽  
pp. 1-9
Author(s):  
Stephen A. Veitch ◽  
Marianne Karplus ◽  
Galen Kaip ◽  
Lucia F. Gonzalez ◽  
Jason M. Amundson ◽  
...  

Abstract Lemon Creek Glacier, a temperate valley glacier in the Juneau Icefield of Southeast Alaska, is the site of long running (>60 years) glaciological studies. However, the most recent published estimates of its thickness and subglacial topography come from two ~50 years old sources that are not in agreement and do not account for the effects of years of negative mass balance. We collected a 1-km long active-source seismic line on the upper section of the glacier parallel and near to the centerline of the glacier, roughly straddling the equilibrium-line altitude. We used these data to perform joint reflection-refraction velocity modeling and reflection imaging of the glacier bed. We find that this upper section of Lemon Creek Glacier is as much as 150 m (~65%) thicker than previously suggested with a large overdeepening in an area previously believed to have a uniform thickness. Our results lead us to reinterpret the impact of basal motion on ice flow and have a significant impact on expectations of subglacial hydrology. We suggest that further efforts to develop a whole-glacier model of subglacial topography are necessary to support studies that require accurate models of ice thickness and subglacial topography.


2021 ◽  
Author(s):  
Xiaowen Wang ◽  
Lin Liu ◽  
Yan Hu ◽  
Tonghua Wu ◽  
Lin Zhao ◽  
...  

Abstract. Collapses of large parts of low-angle mountain glaciers in recent years have raised great attention due to their threats to lives and properties downstream. While current studies have mainly focused on post-event analysis, assessing the potential hazard of glaciers prone to collapse is rare. Here we presented a comprehensive analysis of the dynamics and runout hazard of a low-angle (~ 20°) valley glacier, close to the Qinghai–Tibet railway and highway, in the Kunlun Pass of East Kunlun Mountains on the Qinghai–Tibet Plateau. The changes in morphology, terminus position, and surface elevation of the glacier between 1975 and 2019 were characterized with multi-sensor remote sensing data including a stereo-image pair from the historical KH-9 spy satellite, six Digital Elevation Models (DEMs), and nine high-resolution images from Planet Labs. The surface flow velocities of the glacier tongue between 2009 and 2019 were also tracked based on cross-correlation of Planet images. Our observations show that the glacier snout has been progressively advancing in recent four decades, with a stepwise increase of advance velocity from 4.25 ± 0.28 m a−1 between 1975 and 2009 to 32.53 ± 4.45 m a−1 between 2015 and 2019. DEM differencing confirms the glacial advance, with surface thinning in the source region and thickening in the tongue region. The net volume loss over the glacier tongue was about 11.21 ± 2.66 × 105 m3 during 1975–2019. Image cross-correlation reveals that the surface flow velocity of the glacier tongue has been increasing in recent years, with the mean velocity below 4800 m almost trebled from 22 ± 4 cm a−1 during 2009–2012 to 61 ± 5 cm a−1 during 2016–2019. Piecing these observations together, we suggest that the flow of the glacier tongue is mainly controlled by the geometry of the glacier, while the presence of an ice-dammed lake and a supraglacial pond implies a hydrological influence as well. Taking the glacier tongue as an avalanche source, we quantitively simulated the potential runout distance using the Voellmy–Salm avalanche model. The simulations predict that the avalanche of the glacier tongue will result in a maximum runout distance of about 1.3 km with moderate friction parameters, unlikely to threaten the safety of the Qinghai–Tibet railway.


Quaternary ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 9
Author(s):  
James Innes ◽  
Wishart Mitchell ◽  
Charlotte O’Brien ◽  
David Roberts ◽  
Mairead Rutherford ◽  
...  

The lower reaches of the River Ure, on the flanks of the Pennine Hills in northern England, contain sedimentary and erosional landforms that are a record of fluvial activity during deglaciation and valley-glacier retreat at the end of the last (Devensian) glacial period, and in the subsequent post-glacial Holocene. Terraces and channels, most of which are now relict features well above the altitude of the present river, attest to the impacts of massive meltwater discharge and deposition of sand and gravel outwash, and dynamic river regimes with rapid incision. Through field survey, we have created a detailed geomorphological map of these landforms and glacial and fluvioglacial surface deposits, as well as the terraces and palaeochannels that were abandoned by the river due to avulsion and incision-driven course changes. We have recorded the nature of the outwash gravels, now effectively terrace features, from exposed sections in working quarries, one of which we discuss here. The palaeochannels have accumulated sediment fills and we have examined several which lie within the range of 100 and 16 m above present sea level. The results of lithostratigraphic, palynological, and radiocarbon analyses at two main and three subsidiary sites indicate that palaeochannel ages range from almost 14,000 to approximately 4000 calibrated years ago in a clear altitudinal sequence. The oldest are probably caused by rapid incision due to deglaciation-driven isostatic uplift. The similarity in date of the three downstream sites suggests that a late Holocene combination of climatic deterioration and increased human activity in the catchment caused instability and entrenchment. Pollen data from the channel fills provide relative dating, and agree well with pollen records from other regional Lateglacial and Holocene sites. Non-pollen palynomorph (NPP) analysis at one of the sites allows reconstruction of the hydrological history of channel infill. This research shows that the application of an integrated suite of research techniques can yield a highly detailed understanding of fluvial evolution and landscape history.


2021 ◽  
Author(s):  
Per Holmlund ◽  
Nina Kirchner ◽  
Erik Mannerfelt

<p>Isfallsglaciären in Northern Sweden is a steep polythermal valley glacier located in the Kebnekaise Mountains, which is well studied and thoroughly observed because its proximity to Tarfala Research Station run by Stockholm University. Isfallsglaciären is also included in the Swedish monitoring program for glaciers reported to WGMS.</p><p>The glacier advanced during the 1990s, but continues to recede and thin at a high rate since the turn of the century. On August 26, 2018, a 5x 10<sup>5</sup> m<sup>3  </sup>large portion of Isfallsglaciärens ice tongue decoupled from the main glacier and began to slide down-valley. Within 5 days, a 50 m wide gap had formed which increased to a width of c. 80 m later during the autumn. The front of the decoupled ice section advanced 50 m (timeframe?) over moderately inclined bed topography, and came eventually to a halt, without developing into an ice avalanche. The upstream cliff of the main glacier advanced first at a high rate and then progressively slowed down forming a new glacier front. [NK1] </p><p>The event is very well documented by recurrent aerial photography taken during 2016-2020, as well as more frequent inage acquisition a few weeks before, and shortly after, the event. The photos have been analyzed using structure-from-motion photogrammetry to reveal the magnitude of change at a decimeter-level.</p><p>Departing from a description of this event, we discuss the impact of hazardous changes on glaciers becoming steeper and thinner due to recession, as well as complications arising for glacier front monitoring as part of the WGMS program.</p><p>Similar events have been reported at glaciers elsewhere in Sweden but these events are less well documented and do not influence the monitoring program. In this paper we will describe how data have been handled and inspire to similar studies in any glacier area. We will also discuss the issue in a glacier monitoring perspective.</p>


2020 ◽  
Author(s):  
Edwin Loarte ◽  
Katy Medina ◽  
Yadira Curo ◽  
Hairo Leon ◽  
Fiorella Quiñonez ◽  
...  

<p>One of the effects of climate change on tropical glaciers is the accelerated reduction of their glacial tongue, reflected in a morphometric variation. Many glaciers that had pronounced tongues and that extended through a valley (Valley glacier) now have reduced their fronts located in the upper parts of the valleys (Mountain glacier).</p><p>This has been studied with glaciers of Peru located in 18 mountain ranges located from S 8°20'56" to 15°53'26" and W 77°56'10" to 69°05'14", which are an important solid water reserve that directly supplies the population of 11 departments.</p><p>The study focused on the "digit 1" (primary classification) of the Global Land Ice Measurement from Space (GLIMS), which classifies the glaciers mainly in: valley glaciers and mountain glaciers. The processing of raster and vector data through the use of geographic information system and remote sensing tools allowed to analyze the changes and variations affecting glaciers with respect to their morphometry. For this, a comparison was made between glacier coverage in 2016 (using images Sentinel 2), produced by INAIGEM, and the baseline of the glacier coverage of 1955 and 1970 (using aerial photography), from the first inventory of glaciers in Peru, produced by Hidrandina S.A.</p><p>The results show a significant morphometric variation of 83.7%, where valley glaciers (from Hidrandina inventory) became mainly mountain glaciers. Nowadays only four mountain ranges have mountain glaciers inside whereas in the past it were nine. When we analyze the results for watersheds, the most morphometric changes were 89% in the Atlantic watershed, followed by 57% in the Pacific watershed; in the Amazon watershed there was not any registration of any mountain glaciers since the first inventory in Peru. The surface changes do not show specific any predominant aspect, and average slopes are between 25° and 50°.</p><p>The glacial tongues that are considered valley glacier area located in ablation zones, where the mass balance is negative and there is more susceptibility to reducing their mass and, consequently, to variations in shape and size in a short period. This change has been accentuated in recent decades.</p>


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