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Tracking retreat processes at the Falljökull Glacier, SE Iceland

Tomkins, Matt (2017) Tracking retreat processes at the Falljökull Glacier, SE Iceland. Masters thesis, .

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    Abstract

    In glacial systems, hydrological forcing of ice velocity may lead to instability and accelerated mass loss. However, recent studies have demonstrated that the relationship between ice melt and ice dynamics is non-linear because subglacial drainage configuration strongly modulates meltwater inputs and results in asynchroneity between surface melt production and ice movement. Furthermore, subglacial drainage undergoes temporal evolution and can vary spatially between and within individual glaciers. As such, the degree of connectivity between ice melt and ice dynamics exhibits spatio-temporal variability. To address this, time-lapse images from Falljökull, SE Iceland, were analysed using Pointcatcher, a feature tracking software. Surface velocities and thinning rates were quantified for the period 2011-2013 and compared to results from energy balance modelling (EBM) to determine the climatic, hydrological and structural controls on glacier dynamics. The results show that melt production at Falljökull is closely linked to energy inputs to the glacier surface, although consistent thinning underestimation by the EBM, equivalent to ~1-3 m, reflects the poor optimisation of the model for thin debris cover. In addition, melt production is strongly modulated by individual events e.g. Grímsvötn eruption, which modify surface conditions and enhance/supress melt. A clear relationship between ice melt and ice dynamics is also evident in these data although subglacial drainage structure i.e. discrete/distributed, and surface conditions e.g. debris or snow cover, account for periods of de-coupling. Hydrologically induced speed-up events are identified and occur more readily when inefficient distributed systems are present. In contrast, flow variability is markedly reduced when meltwater inputs are suppressed and when efficient discrete drainage is present. Enhanced flow is strongly linked to sliding at the ice-bed interface although this varies spatially and temporally as a function of subglacial drainage configuration. Finally, these data conflict markedly with previous research which inferred that Falljökull was stagnant and wasting away in-situ. Instead, Falljökull is ‘active’ with movement through ice deformation, basal sliding and subglacial deformation although forward motion is insufficient to offset retreat.

    Item Type: Thesis (Masters)
    Subjects:
    Departments: Faculty of Science and Technology > Lancaster Environment Centre
    ID Code: 84493
    Deposited By: ep_importer_pure
    Deposited On: 01 Feb 2017 12:02
    Refereed?: No
    Published?: Published
    Last Modified: 12 Oct 2017 00:07
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/84493

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