Physical conditions of fast glacier flow: 3. Seasonally-evolving ice deformation on Store Glacier, West Greenland

Young, T. J. and Christoffersen, P. and Doyle, S. H. and Nicholls, K. W. and Stewart, C. L. and Hubbard, B. and Hubbard, A. and Lok, L. B. and Brennan, P. and Benn, D. I. and Luckman, A. and Bougamont, M. (2019) Physical conditions of fast glacier flow: 3. Seasonally-evolving ice deformation on Store Glacier, West Greenland. Journal of Geophysical Research: Earth Surface, 124. pp. 245-267. ISSN 2169-9011

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Abstract

Temporal variations in ice sheet flow directly impact the internal structure within ice sheets through englacial deformation. Large‐scale changes in the vertical stratigraphy within ice sheets have been previously conducted on centennial to millennial timescales; however, intra‐annual changes in the morphology of internal layers have yet to be explored. Over a period of two years, we use autonomous phase‐sensitive radio‐echo sounding (ApRES) to track the daily displacement of internal layers on Store Glacier, West Greenland to millimeter accuracy. At a site located ∼30 km from the calving terminus, where the ice is ∼600m thick and flows at ∼700m a−1, we measure distinct seasonal variations in vertical velocities and vertical strain rates over a two‐year period. Prior to the melt season (March–June), we observe increasingly non‐linear englacial deformation with negative vertical strain rates (i.e. strain thinning) in the upper half of the ice column of ∼‐0.03a−1, whereas the ice below thickens under vertical strain reaching up to 0.16a−1. Early in the melt season (June–July), vertical thinning gradually ceases as the glacier increasingly thickens. During late summer to midwinter (August–February), vertical thickening occurs linearly throughout the entire ice column, with strain rates averaging 0.016a−1. We show that these complex variations are unrelated to topographic setting and localized basal slip, and hypothesize that this seasonality is driven by far‐field perturbations in the glacier's force balance, in this case generated by variations in basal hydrology near the glacier's terminus and propagated tens of kilometers upstream through longitudinal coupling.

Item Type:
Journal Article
Journal or Publication Title:
Journal of Geophysical Research: Earth Surface
Additional Information:
An edited version of this paper was published by AGU. Copyright 2018 American Geophysical Union. Young, T.J. et al.. (2019), Physical conditions of fast glacier flow: 3. Seasonally‐evolving ice deformation on Store Glacier, West Greenland, J. Geophys. Res. Earth Surf., 124. https://doi.org/10.1029/2018JF004821 To view the published open abstract, go to http://dx.doi.org/10.1029/2018JF004821
ID Code:
130533
Deposited By:
Deposited On:
17 Jan 2019 14:20
Refereed?:
Yes
Published?:
Published
Last Modified:
27 Sep 2020 05:02