Journal: The Cryosphere Discussions

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Copernicus

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1994-0432
1994-0440

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2015 - 201972020 - 20224
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Publications 1 - 10 of 11
  • Greenland and Canadian Arctic ice temperature profiles
    Item type: Working Paper
    Løkkegaard, Anja; Mankoff, Kenneth; Zdanowicz, Christian; et al. (2022)
    The Cryosphere Discussions
    Here, we present a compilation of 85 ice temperature profiles from 79 boreholes from the Greenland Ice Sheet and peripheral ice caps, as well as local ice caps in the Canadian Arctic. Only 25 profiles (32 %) were previously available in open-access data repositories. The remaining 54 profiles (68 %) are being made digitally available here for the first time. These newly available profiles, which are associated with pre-2010 boreholes, have been submitted by community members or digitized from published graphics and/or data tables. All 85 profiles are now made available in both absolute (meters) and normalized (0 to 1 ice thickness) depth scales, and are accompanied by extensive metadata. This metadata includes a transparent description of data provenance. The ice temperature profiles span 70 years, with the earliest profile being from 1950 at Camp VI, West Greenland. To highlight the value of this database in evaluating ice flow simulations, we compare the ice temperature profiles from the Greenland Ice Sheet with an ice flow simulation by the Parallel Ice Sheet Model (PISM). We find a cold bias in modeled near-surface ice temperatures within the ablation area, a warm bias in modeled basal ice temperatures at inland cold-bedded sites, and an apparent underestimation of deformational heating in high-strain settings. These biases provide process-level insight on simulated ice temperatures.
  • Glaciohydraulic seismic tremors on an Alpine glacier
    Item type: Working Paper
    Lindner, Fabian; Walter, Fabian; Laske, Gabi; et al. (2019)
    The Cryosphere Discussions
    Hydraulic processes impact viscous and brittle ice deformation. Water-driven fracturing as well as turbulent waterflow within and beneath glaciers radiate seismic waves which provide insights into otherwise hard-to-access englacial and subglacial environments. In this study, we analyze glaciohydraulic tremors recorded by four seismic arrays installed in different parts of Glacier de la Plaine Morte, Switzerland. Data were recorded during the 2016 melt season including the sudden subglacial drainage of an ice-marginal lake. Together with our seismic data, discharge, lake level, and ice flow measurements provide constraints on glacier hydraulics. We find that the tremors are generated by subglacial water flow, in moulins, and byicequake bursts. The dominating process can vary on sub-kilometer and sub-daily scales. Consistent with field observations,continuous source tracking via matched-field processing suggests a gradual upglacier progression of an efficient drainage sys-tem as the melt season progresses. The ice-marginal lake likely connects to this drainage system via hydrofracturing, whichis indicated by sustained icequake signals emitted from the proximity of the lake basin and starting roughly 24 hours prior to the lake drainage. To estimate the hydraulics associated with the drainage, we use tremor-discharge scaling relationships. Our analysis suggests a pressurization of the subglacial environment at the drainage onset, followed by an increase in the hydraulicradii of the conduits and a subsequent decrease in the subglacial water pressure as the capacity of the drainage system increases.The pressurization is in phase with the drop in the lake level and its retrieved maximum coincides with ice-uplift measured via GPS. Our results highlight the use of cryo-seismology for monitoring glacier hydraulics
  • Initiation of a major calving event on Bowdoin Glacier captured by UAV photogrammetry
    Item type: Working Paper
    Jouvet, Guillaume; Weidmann, Yvo; Seguinot, Julien; et al. (2016)
    The Cryosphere Discussions
  • Resolving the influence of temperature forcing through heat conduction on rockglacier dynamics: a numerical modelling approach
    Item type: Working Paper
    Cicoira, Alessandro; Beutel, Jan; Faillettaz, Jérôme; et al. (2018)
    The Cryosphere Discussions
    In recent years, observations have highlighted seasonal and inter-annual variability in rockglacier flow. Temperature forcing, through heat conduction, has been proposed as one of the key processes to explain these variations in kinematics. However, this mechanism has not yet been quantitatively assessed against real-world data. We present a 1-D numerical modelling approach that couples heat conduction to an empirically derived creep model for ice-rich frozen soils. We use this model to investigate the effect of thermal heat conduction on seasonal and inter-annual variability in rockglacier flow. We compare the model results with borehole temperature data and surface velocity measurements from the PERMOS and PermaSense monitoring network in the Swiss Alps. We further conduct a model sensitivity analysis in order to resolve the importance of the different model parameters. Using the prescribed empirically derived rheology and observed near-surface temperatures, we are able to model the right order of magnitude of creep flow. However, both inter-annual and seasonal variability are underestimated by an order of magnitude, implying that heat conduction alone can not explain the observed variations. Therefore, non-conductive processes, likely linked to water availability, dominate the short-term velocity signal.
  • Modelling supraglacial debris-cover evolution from the single glacier to the regional scale: an application to High Mountain Asia
    Item type: Working Paper
    Compagno, Loris; Huss, Matthias; Miles, Evan S.; et al. (2021)
    The Cryosphere Discussions
    Currently, about 12–13 % of High Mountain Asia's glacier area is debris-covered, altering its surface mass balance. However, in regional-scale modelling approaches, debris-covered glaciers are typically treated as clean-ice glaciers, leading to a potential bias when modelling their future evolution. Here, we present a new approach for modelling debris area and thickness evolution, applicable from single glaciers to the global scale. We implement the module into the Global Glacier Evolution Model (GloGEMflow), a combined mass-balance ice-flow model. The module is initialized with both glacier-specific observations of the debris’ spatial distribution and estimates of debris thickness, accounts for the fact that debris can either enhance or reduce surface melt depending on thickness, and enables representing the spatio-temporal evolution of debris extent and thickness. We calibrate and evaluate the module on a select subset of glaciers, and apply the model using different climate scenarios to project the future evolution of all glaciers in High Mountain Asia until 2100. Compared to 2020, total glacier volume is expected to decrease by between 35 ± 15 % and 80 ±11 %, which is in line with projections in the literature. Depending on the scenario, the mean debris-cover fraction is expected to increase, while mean debris thickness is modelled to show only minor changes, albeit large local thickening is expected. To isolate the influence of explicitly accounting for supraglacial debris-cover, we re-compute glacier evolution without the debris-cover module. We show that glacier geometry, area, volume and flow velocity evolve differently, especially at the level of individual glaciers. This highlights the importance of accounting for debris-cover and its spatio-temporal evolution when projecting future glacier changes.
  • How accurate are estimates of glacier ice thickness? Results from ITMIX, the Ice Thickness Models Intercomparison eXperiment
    Item type: Working Paper
    Farinotti, Daniel; Brinkerhoff, Douglas J.; Clarke, Garry K.C.; et al. (2016)
    The Cryosphere Discussions
  • Brief communication: Do 1.0 °C, 1.5 °C or 2.0 °C matter for the future evolution of Alpine glaciers?
    Item type: Working Paper
    Compagno, Loris; Eggs, Sarah; Huss, Matthias; et al. (2021)
    The Cryosphere Discussions
    With the Paris Agreement, the urgency of limiting ongoing anthropogenic climate change has been recognized. More recent discussions have focused on the difference of limiting the increase in global average temperatures below 1.0, 1.5, or 2.0 °C compared to pre-industrial 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 5 have important implications for the changes predicted until 2100, and that glaciers might start recovering after the end of the 21st century.
  • Halving of Swiss glacier volume since 1931 observed from terrestrial image photogrammetry
    Item type: Working Paper
    Schytt Holmlund, Erik Karl Eldar; Dehecq, Amaury; Hugonnet, Romain; et al. (2022)
    The Cryosphere Discussions
    The monitoring of glaciers in Switzerland has a long tradition, yet glacier changes during the 20th century are only known through sparse observations. Here, we estimate a halving of Swiss glacier volumes between 1931 and 2016 by mapping historical glacier elevation changes at high resolution. Our analysis relies on a terrestrial image archive known as TerrA, which covers about 86 % of the Swiss glacierised area with 21,703 images acquired during the period 1916–1947 (1931 on average). We developed a semi-automated workflow to generate digital elevation models (DEMs) from these images, resulting in a 45 % total glacier coverage. Using the geodetic method, we estimate a Swiss-wide glacier mass balance of –0.52 ± 0.09 m w.e. a−1 between 1931 and 2016. This equates to a 51.5 ± 6.1 % loss in glacier volume. We find that low elevation, high debris cover, and gently sloping glacier termini are conductive to particularly high mass losses. In addition to these glacier-specific, quasi- centennial elevation changes, we present a new inventory of glacier outlines with known timestamps and complete attributes from around 1931. The fragmented spatial coverage and temporal heterogeneity of the TerrA archive are the largest sources of uncertainty in our glacier-specific estimates, reaching up to 0.50 m w.e. a−1. We suggest that the high-resolution mapping of historic surface elevations could unlock great potentials also for research fields other than glaciology.
  • Tomography-based observation of sublimation and snow metamorphism under temperature gradient and advective flow
    Item type: Working Paper
    Ebner, Pirmin; Schneebeli, Martin; Steinfeld, Aldo (2015)
    The Cryosphere Discussions
  • Anisotropy of seasonal snow measured by polarimetric phase differences in radar time series
    Item type: Working Paper
    Leinss, Silvan; Löwe, Henning; Proksch, Martin; et al. (2015)
    The Cryosphere Discussions
Publications 1 - 10 of 11