Articles | Volume 15, issue 1
https://doi.org/10.5194/tc-15-265-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-15-265-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
19 Jan 2021
Research article |
| 19 Jan 2021
| 19 Jan 2021
Debris cover and the thinning of Kennicott Glacier, Alaska: in situ measurements, automated ice cliff delineation and distributed melt estimates
Department of Geological Sciences and Institute of Arctic and Alpine
Research, University of Colorado Campus Box 450, Boulder, CO 80309-0450, USA
GFZ German Research Centre for Geosciences, Telegrafenberg, 14473
Potsdam, Germany
William H. Armstrong
Department of Geological Sciences and Institute of Arctic and Alpine
Research, University of Colorado Campus Box 450, Boulder, CO 80309-0450, USA
Department of Geological and Environmental Sciences, Appalachian State
University, 033 Rankin Science West, ASU Box 32067, Boone, NC 28608-2067,
USA
Robert S. Anderson
Department of Geological Sciences and Institute of Arctic and Alpine
Research, University of Colorado Campus Box 450, Boulder, CO 80309-0450, USA
Pascal Buri
Geophysical Institute, University of Alaska-Fairbanks, 2156 Koyukuk
Drive, Fairbanks, AK 99775, USA
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Thick rock cover (or debris) disturbs the melt of many Alaskan glaciers. Yet the effect of debris on glacier thinning in Alaska has been overlooked. In three companion papers we assess the role of debris and ice flow on the thinning of Kennicott Glacier. In Part C we describe feedbacks contributing to rapid thinning under thick debris. Changes in debris thickness downglacier on Kennicott Glacier are manifested in the pattern of glacier thinning, ice dynamics, melt, and glacier surface features.
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The Cryosphere, 11, 1501–1517, https://doi.org/10.5194/tc-11-1501-2017, https://doi.org/10.5194/tc-11-1501-2017, 2017
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Sub-meter satellite stereo images (Pléiades and WorldView2) are used to accurately measure snow accumulation and winter mass balance of Drangajökull ice cap. This is done by creating and comparing accurate digital elevation models. A glacier-wide geodetic mass balance of 3.33 ± 0.23 m w.e. is derived between October 2014 and May 2015. This method could be easily transposable to remote glaciated areas where seasonal mass balance measurements (especially winter accumulation) are lacking.
Leif S. Anderson and Robert S. Anderson
The Cryosphere, 10, 1105–1124, https://doi.org/10.5194/tc-10-1105-2016, https://doi.org/10.5194/tc-10-1105-2016, 2016
Short summary
Short summary
Mountains erode and shed rocks down slope. When these rocks (debris) fall on glacier ice they can suppress ice melt. By protecting glaciers from melt, debris can make glaciers extend to lower elevations. Using mathematical models of glaciers and debris deposition, we find that debris can more than double the length of glaciers. The amount of debris deposited on the glacier, which scales with mountain height and steepness, is the most important control on debris-covered glacier length and volume.
K. R. Barnhart, I. Overeem, and R. S. Anderson
The Cryosphere, 8, 1777–1799, https://doi.org/10.5194/tc-8-1777-2014, https://doi.org/10.5194/tc-8-1777-2014, 2014
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Temperature-index models have been widely used for glacier mass projections in the future. The ability of these models to capture non-linear responses of glacier mass balance (MB) to high deviations in air temperature and solid precipitation has recently been questioned by mass balance simulations employing advanced machine-learning techniques. Here, we confirmed that temperature-index models are capable of detecting non-linear responses of glacier MB to temperature and precipitation changes.
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The new Caucasus glacier inventory derived from manual delineation of glacier outlines based on medium-resolution (Landsat, Sentinel) and high-resolution (SPOT) satellite imagery shows the accelerated glacier area loss over the last 2 decades (2000–2020). This new glacier inventory will improve our understanding of climate change impacts at a regional scale and support related modelling studies by providing high-quality validation data.
Alexis Neven, Valentin Dall'Alba, Przemysław Juda, Julien Straubhaar, and Philippe Renard
The Cryosphere, 15, 5169–5186, https://doi.org/10.5194/tc-15-5169-2021, https://doi.org/10.5194/tc-15-5169-2021, 2021
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We present and compare different geostatistical methods for underglacial bedrock interpolation. Variogram-based interpolations are compared with a multipoint statistics approach on both test cases and real glaciers. Using the modeled bedrock, the ice volume for the Scex Rouge and Tsanfleuron glaciers (Swiss Alps) was estimated to be 113.9 ± 1.6 million cubic meters. Complex karstic geomorphological features are reproduced and can be used to improve the precision of underglacial flow estimation.
Daniela Festi, Margit Schwikowski, Valter Maggi, Klaus Oeggl, and Theo Manuel Jenk
The Cryosphere, 15, 4135–4143, https://doi.org/10.5194/tc-15-4135-2021, https://doi.org/10.5194/tc-15-4135-2021, 2021
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In our study we dated a 46 m deep ice core retrieved from the Adamello glacier (Central Italian Alps). We obtained a timescale combining the results of radionuclides 210Pb and 137Cs with annual layer counting derived from pollen and refractory black carbon concentrations. Our results indicate that the surface of the glacier is older than the drilling date of 2016 by about 20 years, therefore revealing that the glacier is at high risk of collapsing under current climate warming conditions.
Loris Compagno, Sarah Eggs, Matthias Huss, Harry Zekollari, and Daniel Farinotti
The Cryosphere, 15, 2593–2599, https://doi.org/10.5194/tc-15-2593-2021, https://doi.org/10.5194/tc-15-2593-2021, 2021
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Recently, discussions have focused on the difference in limiting the increase in global average temperatures to below 1.0, 1.5, or 2.0 °C compared to preindustrial levels. Here, we assess the impacts that such different scenarios would have on both the future evolution of glaciers in the European Alps and the water resources they provide. Our results show that the different temperature targets have important implications for the changes predicted until 2100.
Dahong Zhang, Xiaojun Yao, Hongyu Duan, Shiyin Liu, Wanqin Guo, Meiping Sun, and Dazhi Li
The Cryosphere, 15, 1955–1973, https://doi.org/10.5194/tc-15-1955-2021, https://doi.org/10.5194/tc-15-1955-2021, 2021
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Glacier centerlines are crucial input for many glaciological applications. We propose a new algorithm to derive glacier centerlines and implement the corresponding program in Python language. Application of this method to 48 571 glaciers in the second Chinese glacier inventory automatically yielded the corresponding glacier centerlines with an average computing time of 20.96 s, a success rate of 100 % and a comprehensive accuracy of 94.34 %.
Livia Jakob, Noel Gourmelen, Martin Ewart, and Stephen Plummer
The Cryosphere, 15, 1845–1862, https://doi.org/10.5194/tc-15-1845-2021, https://doi.org/10.5194/tc-15-1845-2021, 2021
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Glaciers and ice caps are currently the largest contributor to sea level rise. Global monitoring of these regions is a challenging task, and significant differences remain between current estimates. This study looks at glacier changes in High Mountain Asia and the Gulf of Alaska using a new technique, which for the first time makes the use of satellite radar altimetry for mapping ice mass loss over mountain glacier regions possible.
Sebastian Hellmann, Johanna Kerch, Ilka Weikusat, Andreas Bauder, Melchior Grab, Guillaume Jouvet, Margit Schwikowski, and Hansruedi Maurer
The Cryosphere, 15, 677–694, https://doi.org/10.5194/tc-15-677-2021, https://doi.org/10.5194/tc-15-677-2021, 2021
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We analyse the orientation of ice crystals in an Alpine glacier and compare this orientation with the ice flow direction. We found that the crystals orient in the direction of the largest stress which is in the flow direction in the upper parts of the glacier and in the vertical direction for deeper zones of the glacier. The grains cluster around this maximum stress direction, in particular four-point maxima, most likely as a result of recrystallisation under relatively warm conditions.
Lea Hartl, Lucia Felbauer, Gabriele Schwaizer, and Andrea Fischer
The Cryosphere, 14, 4063–4081, https://doi.org/10.5194/tc-14-4063-2020, https://doi.org/10.5194/tc-14-4063-2020, 2020
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When glaciers become snow-free in summer, darker glacier ice is exposed. The ice surface is darker than snow and absorbs more radiation, which increases ice melt. We measured how much radiation is reflected at different wavelengths in the ablation zone of Jamtalferner, Austria. Due to impurities and water on the ice surface there are large variations in reflectance. Landsat 8 and Sentinel-2 surface reflectance products do not capture the full range of reflectance found on the glacier.
Vincent Peyaud, Coline Bouchayer, Olivier Gagliardini, Christian Vincent, Fabien Gillet-Chaulet, Delphine Six, and Olivier Laarman
The Cryosphere, 14, 3979–3994, https://doi.org/10.5194/tc-14-3979-2020, https://doi.org/10.5194/tc-14-3979-2020, 2020
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Alpine glaciers are retreating at an accelerating rate in a warming climate. Numerical models allow us to study and anticipate these changes, but the performance of a model is difficult to evaluate. So we compared an ice flow model with the long dataset of observations obtained between 1979 and 2015 on Mer de Glace (Mont Blanc area). The model accurately reconstructs the past evolution of the glacier. We simulate the future evolution of Mer de Glace; it could retreat by 2 to 6 km by 2050.
Gregory Church, Melchior Grab, Cédric Schmelzbach, Andreas Bauder, and Hansruedi Maurer
The Cryosphere, 14, 3269–3286, https://doi.org/10.5194/tc-14-3269-2020, https://doi.org/10.5194/tc-14-3269-2020, 2020
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In this field study, we repeated ground-penetrating radar measurements over an active englacial channel network that transports meltwater through the glacier. We successfully imaged the englacial meltwater pathway and were able to delimitate the channel's shape. Meltwater from the glacier can impact the glacier's dynamics if it reaches the ice–bed interface, and therefore monitoring these englacial drainage networks is important to understand how these networks behave throughout a season.
Argha Banerjee, Disha Patil, and Ajinkya Jadhav
The Cryosphere, 14, 3235–3247, https://doi.org/10.5194/tc-14-3235-2020, https://doi.org/10.5194/tc-14-3235-2020, 2020
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Simple models of glacier dynamics based on volume–area scaling underestimate climate sensitivity and response time of glaciers. Consequently, they may predict a faster response and a smaller long-term glacier loss. These biases in scaling models are established theoretically and are analysed in detail by simulating the step response of a set of 703 Himalayan glaciers separately by three different models: a scaling model, a 2-D shallow-ice approximation model, and a linear-response model.
Junfeng Liu, Rensheng Chen, and Chuntan Han
The Cryosphere, 14, 967–984, https://doi.org/10.5194/tc-14-967-2020, https://doi.org/10.5194/tc-14-967-2020, 2020
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Glacier surface roughness during melting season was observed by manual and automatic photogrammetry. Surface roughness was larger at the snow and ice transition zone than in fully snow- or ice-covered areas. Persistent snowfall and rainfall both reduce surface roughness. High or rising turbulent heat as a component of surface energy balance tended to produce a smooth ice surface; low or decreasing turbulent heat tended to produce a rougher surface.
Christian Vincent, Adrien Gilbert, Bruno Jourdain, Luc Piard, Patrick Ginot, Vladimir Mikhalenko, Philippe Possenti, Emmanuel Le Meur, Olivier Laarman, and Delphine Six
The Cryosphere, 14, 925–934, https://doi.org/10.5194/tc-14-925-2020, https://doi.org/10.5194/tc-14-925-2020, 2020
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We observed very low glacier thickness changes over the last decades at very-high-elevation glaciated areas on Mont Blanc. Conversely, measurements performed in deep boreholes since 1994 reveal strong changes in englacial temperature reaching 1.5 °C at a depth of 50 m. We conclude that at such very high elevations, current changes in climate do not lead to visible changes in glacier thickness but cause invisible changes within the glacier in terms of englacial temperatures.
Levan G. Tielidze, Tobias Bolch, Roger D. Wheate, Stanislav S. Kutuzov, Ivan I. Lavrentiev, and Michael Zemp
The Cryosphere, 14, 585–598, https://doi.org/10.5194/tc-14-585-2020, https://doi.org/10.5194/tc-14-585-2020, 2020
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We present data of supra-glacial debris cover for 659 glaciers across the Greater Caucasus based on satellite images from the years 1986, 2000 and 2014. We combined semi-automated methods for mapping the clean ice with manual digitization of debris-covered glacier parts and calculated supra-glacial debris-covered area as the residual between these two maps. The distribution of the supra-glacial debris cover differs between northern and southern and between western, central and eastern Caucasus.
Lisbeth Langhammer, Melchior Grab, Andreas Bauder, and Hansruedi Maurer
The Cryosphere, 13, 2189–2202, https://doi.org/10.5194/tc-13-2189-2019, https://doi.org/10.5194/tc-13-2189-2019, 2019
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We have developed a novel procedure for glacier thickness estimations that combines traditional glaciological modeling constraints with ground-truth data, for example, those obtained with ground-penetrating radar (GPR) measurements. This procedure is very useful for determining ice volume when only limited data are available. Furthermore, we outline a strategy for acquiring GPR data on glaciers, such that the cost/benefit ratio is optimized.
Nico Mölg, Tobias Bolch, Andrea Walter, and Andreas Vieli
The Cryosphere, 13, 1889–1909, https://doi.org/10.5194/tc-13-1889-2019, https://doi.org/10.5194/tc-13-1889-2019, 2019
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Debris can partly protect glaciers from melting. But many debris-covered glaciers change similar to debris-free glaciers. To better understand the debris influence we investigated 150 years of evolution of Zmutt Glacier in Switzerland. We found an increase in debris extent over time and a link to glacier flow velocity changes. We also found an influence of debris on the melt locally, but only a small volume change reduction over the whole glacier, also because of the influence of ice cliffs.
Harry Zekollari, Matthias Huss, and Daniel Farinotti
The Cryosphere, 13, 1125–1146, https://doi.org/10.5194/tc-13-1125-2019, https://doi.org/10.5194/tc-13-1125-2019, 2019
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Glaciers in the European Alps play an important role in the hydrological cycle, act as a source for hydroelectricity and have a large touristic importance. We model the future evolution of all glaciers in the Alps with a novel model that combines both ice flow and melt processes. We find that under a limited warming scenario about one-third of the present-day ice volume will still be present by the end of the century, while under strong warming more than 90 % of the volume will be lost by 2100.
Tobias Zolles, Fabien Maussion, Stephan Peter Galos, Wolfgang Gurgiser, and Lindsey Nicholson
The Cryosphere, 13, 469–489, https://doi.org/10.5194/tc-13-469-2019, https://doi.org/10.5194/tc-13-469-2019, 2019
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A mass and energy balance model was subjected to sensitivity and uncertainty analysis on two different Alpine glaciers. The global sensitivity analysis allowed for a mass balance measurement independent assessment of the model sensitivity and functioned as a reduction of the model free parameter space. A novel approach of a multi-objective optimization estimates the uncertainty of the simulated mass balance and the energy fluxes. The final model uncertainty is up to 1300 kg m−3 per year.
Matthew Olson and Summer Rupper
The Cryosphere, 13, 29–40, https://doi.org/10.5194/tc-13-29-2019, https://doi.org/10.5194/tc-13-29-2019, 2019
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Solar radiation is the largest energy input for most alpine glaciers. However, many models oversimplify the influence of topographic shading. Also, no systematic studies have explored the variable impact of shading on glacier ice. We find that shading can significantly impact modeled solar radiation, particularly at low elevations, at high latitudes, and for glaciers with a north/south orientation. Excluding the effects of shading will overestimate modeled solar radiation for alpine glaciers.
Michael Sigl, Nerilie J. Abram, Jacopo Gabrieli, Theo M. Jenk, Dimitri Osmont, and Margit Schwikowski
The Cryosphere, 12, 3311–3331, https://doi.org/10.5194/tc-12-3311-2018, https://doi.org/10.5194/tc-12-3311-2018, 2018
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The fast retreat of Alpine glaciers since the mid-19th century documented in photographs is used as a symbol for the human impact on global climate, yet the key driving forces remain elusive. Here we argue that not industrial soot but volcanic eruptions were responsible for an apparently accelerated deglaciation starting in the 1850s. Our findings support a negligible role of human activity in forcing glacier recession at the end of the Little Ice Age, highlighting the role of natural drivers.
Zhiyuan Cong, Shaopeng Gao, Wancang Zhao, Xin Wang, Guangming Wu, Yulan Zhang, Shichang Kang, Yongqin Liu, and Junfeng Ji
The Cryosphere, 12, 3177–3186, https://doi.org/10.5194/tc-12-3177-2018, https://doi.org/10.5194/tc-12-3177-2018, 2018
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Cryoconites from glaciers on the Tibetan Plateau and surrounding area were studied for iron oxides. We found that goethite is the predominant iron oxide form. Using the abundance, speciation and optical properties of iron oxides, the total light absorption was quantitatively attributed to goethite, hematite, black carbon and organic matter. Such findings are essential to understand the relative significance of anthropogenic and natural impacts.
Denis Cohen, Fabien Gillet-Chaulet, Wilfried Haeberli, Horst Machguth, and Urs H. Fischer
The Cryosphere, 12, 2515–2544, https://doi.org/10.5194/tc-12-2515-2018, https://doi.org/10.5194/tc-12-2515-2018, 2018
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As part of an integrative study about the safety of repositories for radioactive waste under ice age conditions in Switzerland, we modeled the flow of ice of the Rhine glacier at the Last Glacial Maximum to determine conditions at the ice–bed interface. Results indicate that portions of the ice lobes were at the melting temperature and ice was sliding, two conditions necessary for erosion by glacier. Conditions at the bed of the ice lobes were affected by climate and also by topography.
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Short summary
Many glaciers are thinning rapidly beneath debris cover (loose rock) that reduces melt, including Kennicott Glacier in Alaska. This contradiction has been explained by melt hotspots, such as ice cliffs, scattered within the debris cover. However, at Kennicott Glacier declining ice flow explains the rapid thinning. Through this study, Kennicott Glacier is now the first glacier in Alaska, and the largest glacier globally, where melt across its debris-covered tongue has been rigorously quantified.
Many glaciers are thinning rapidly beneath debris cover (loose rock) that reduces melt,...
