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  • 2020-2024  (3)
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  • 1
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    The First Stage of Firn Densification ‐ An Evaluation of Grain Boundary Sliding (2021)
    Wiley
    In:  EPIC3PAMM, Wiley, 21(1), ISSN: 1617-7061
    Details
    Publication Date: 2023-10-24
    Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Firn describes the interstage product between snow and ice in cold regions of the earth, where annual snow fall exceeds the amount of snow melting. The continuing accumulation of snow leads to its densificiation due to overburden stress until it becomes ice. In the field of glaciology various attempts on simulating firn densification have been made and new models are still developed, as the knowledge of the firn column's density structure allows important derivations.〈/jats:p〉〈jats:p〉The presented study reassesses a model description for low density firn based on the process of grain boundary sliding presented by Alley in 1987 [1] using an optimisation approach. By comparing simulation results to 159 measured firn density profiles from Greenland and Antarctica it finds a possible additional dependency of the constitutive relation on the mean surface mass balance. This result is interpreted as an insufficient description of the stress regime.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 2
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    Dark Glacier Surface of Greenland’s Largest Floating Tongue Governed by High Local Deposition of Dust (2020)
    MDPI
    In:  EPIC3Remote Sensing, MDPI, 12(22), pp. 3793-3793, ISSN: 2072-4292
    Details
    Publication Date: 2023-10-24
    Description: Surface melt, driven by atmospheric temperatures and albedo, is a strong contribution of mass loss of the Greenland Ice Sheet. In the past, black carbon, algae and other light-absorbing impurities were suggested to govern albedo in Greenland’s ablation zone. Here we combine optical (MODIS/Sentinel-2) and radar (Sentinel-1) remote sensing data with airborne radar and laser scanner data, and engage firn modelling to identify the governing factors leading to dark glacier surfaces in Northeast Greenland. After the drainage of supraglacial lakes, the former lake ground is a clean surface represented by a high reflectance in Sentinel-2 data and aerial photography. These bright spots move with the ice flow and darken by more than 20% over only two years. In contrast, sites further inland do not exhibit this effect. This finding suggests that local deposition of dust, rather than black carbon or cryoconite formation, is the governing factor of albedo of fast-moving outlet glaciers. This is in agreement with a previous field study in the area which finds the mineralogical composition and grain size of the dust comparable with that of the surrounding soils.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 3
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    Modelling the Transformation from Snow to Ice Based on the Underlying Sintering Process (2021)
    Wiley
    In:  EPIC3PAMM, Wiley, 20(1), ISSN: 1617-7061
    Details
    Publication Date: 2023-10-24
    Description: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉In cold regions of the earth, like Antarctica, Greenland or mountains at high altitude, the annual amount of deposited snow exceeds the amount of snow melting. Snow, which is more than one year old, is called firn. Over time firn transforms into ice by a sintering process, mainly driven by overburden pressure and temperature. This ultimately leads to the formation of glaciers and ice sheets.〈/jats:p〉〈jats:p〉We simulate firn densification based on the processes of sintering. The constitutive law represents grain boundary sliding, dislocation creep and diffusion. These mechanisms sum up to the overall densification which leads to the transformation of snow to ice. The model aims at obtaining a physics driven simulation tool for firn densification which provides data for a wider range of areas. It will contribute to develop better models and better understanding of the cryosphere.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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