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Investigating the ratio of basal drag and driving stress in relation to bedrock topography during a melt season on Storglaciären, Sweden, using force budget analysis
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. (Glaciologi)
Department of Physical Geogr aphy and Quaternary Geology , Stockholm University .
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2003 (English)In: Annals of Glaciology, ISSN 0260-3055, Vol. 37, no 1, 263-268 p.Article in journal (Refereed) Published
Abstract [en]

We apply the force-budget technique using the isothermal block-flow model, on Storglacia« ren, Sweden, to investigate the ratio between basal drag and driving stress in relation to a bedrock ridge in the bed topography during a peak melt season. The input data consist of glacier surface velocities collected using differential global positioning system surveying of a stake net and geometry fromprevious radar soundings and digitized ice surface maps. The study focuses on the effects of transverse bedrock ridges upon basal stress conditions.The pattern of the calculated ratio of basal drag and driving stress shows a rhythmical position of relatively high and lowbasal drags onthe stoss and lee sides, respectively, of the bedrock thresholds. One of the zones of low basal drag corresponds to the location where the highest basal sliding rate has been measured previously by borehode deformation studies. This zone also aligns with the area where the drainage system is suggested to change from englacial to subglacial.

Place, publisher, year, edition, pages
2003. Vol. 37, no 1, 263-268 p.
National Category
Earth and Related Environmental Sciences Physical Geography
Identifiers
URN: urn:nbn:se:uu:diva-91612DOI: 10.3189/172756403781815861OAI: oai:DiVA.org:uu-91612DiVA: diva2:164406
Available from: 2004-04-16 Created: 2004-04-16 Last updated: 2013-08-26Bibliographically approved
In thesis
1. Force Budget Analysis of Glacier Flow: Ice Dynamical Studies on Storglaciären, Sweden, and Ice Flow Investigations of Outlet Glaciers in Dronning Maud Land, Antarctica
Open this publication in new window or tab >>Force Budget Analysis of Glacier Flow: Ice Dynamical Studies on Storglaciären, Sweden, and Ice Flow Investigations of Outlet Glaciers in Dronning Maud Land, Antarctica
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Kraftbudgetanalys av glacialt flöde : Isdynamiska studier på Storglaciären, Sverige, och isflödesundersökningar av utlöparglaciärer i Drottning Maud Land, Antarktis
Abstract [en]

This thesis contributes to the understanding of glacier response to climate change by ice dynamical studies on Storglaciären, Sweden, and Bonnevie-Svendsenbreen, Kibergbreen and Plogbreen in Dronning Maud Land, Antarctica. Ice surface velocities, ice geometry and temperature information is fed through a force budget model to calculate ice mass outflux of these glacial systems via three-dimensional stress distributions for a flux-gate.

Field data were collected through repeated DGPS and GPR observations on Storglaciären between July 2000 to September 2001 and on Kibergbreen and Plobreen during the SWEDARP 2002/03 expedition to Antarctica. The work was strongly supported by remotely-sensed information.

The results from Storglaciären show a strength in the force budget model to discern both spatial and temporal variability in ice dynamical patterns. It highlights the influence of seasonality and bedrock topography upon glacier flow. A modeling experiment on Bonnevie-Svendsenbreen suggested that ice temperature increases substantially under conditions of high stress (≥0.4 MPa) due to strain-heating. This provides a positive feedback loop, increasing ice deformation, as long as it overcomes the advection of cool ice from the surface. These results explain, to some extent, the mechanism behind fast flowing ice streams. Mass flux caclulations from Bonnevie-Svendsenbreen suggest that the outflux given from force budget calculations can be used as a gauge for influx assuming steady state conditions. Plogbreen receives an influx of 0.48±0.1 km3 a-1 and expedites a discharge volume of 0.55±0.05 km3 a-1. This indicative negative mass balance is explained by a falling trend in upstream accumulation and the recent rise in global sea level, as it is likely to induce glacier acceleration due to a reduction in resistive forces at the site of the gate. This result is comparable with other Antarctic studies reporting negative mass balances, e.g. from WAIS, as caused by changes in the global atmospheric circulation pattern.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 71 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 963
Keyword
Physical geography and sedimentology, force budget, ice flux, ice dynamics, mass balance, strain heating, climate change, Storglaciären, Dronning Maud Land, Antarctica, Naturgeografi och sedimentologi
National Category
Physical Geography
Identifiers
urn:nbn:se:uu:diva-4219 (URN)91-554-5936-6 (ISBN)
Public defence
2004-05-14, Hambergsalen, Geocentrum, Villavägen 16, 752 36 Uppsala, 10:00
Opponent
Supervisors
Available from: 2004-04-16 Created: 2004-04-16Bibliographically approved

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Hedfors, JimPohjola, Veijo APettersson, Rickard

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