Seasonal dynamic thinning at Helheim Glacier

Suzanne L. Bevan, Adrian Luckman, Shfaqat Abbas Khan, Tavi Murray

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    Abstract

    We investigate three annual mass-balance cycles on Helheim Glacier in south-east Greenland using TanDEM-X interferometric digital elevation models (DEMs), bedrock GPS measurements, and ice velocity from feature-tracking. The DEMs exhibit seasonal surface elevation cycles at elevations up to 800 m.a.s.l. with amplitudes of up to 19 m, from a maximum in July to a minimum in October or November, concentrated on the fast-flowing areas of the glacier indicating that the elevation changes have a mostly dynamic origin. By modelling the detrended bedrock loading/unloading signal we estimate a mean density for the loss of 671±70kgm-3 and calculate that total water equivalent volume loss from the active part of the glacier (surface flow speeds >1 m day-1) ranges from 0.5 km3 in 2011 to 1.6 km3 in 2013. A rough ice-flux divergence analysis shows that at lower elevations (<200 m) mass loss by dynamic thinning fully explains seasonal elevation changes. In addition, surface elevations decrease by a greater amount than field observations of surface ablation or surface-energy-balance modelling predict, emphasising the dynamic nature of the mass loss. We conclude, on the basis of ice-front position observations through the time series, that melt-induced acceleration is most likely the main driver of the seasonal dynamic thinning, as opposed to changes triggered by retreat.
    Original languageEnglish
    JournalEarth and Planetary Science Letters
    Volume415
    Pages (from-to)47-53
    ISSN0012-821X
    DOIs
    Publication statusPublished - 2015

    Bibliographical note

    ©2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license

    Keywords

    • Dynamics
    • Glaciology
    • Helheim Glacier
    • Mass balance
    • TanDEM-X

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