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Polythermal glacier dynamics at Storglaciaren, Arctic Sweden, inferred using in situ geophysical techniques. / Alessio Gusmeroli

Swansea University Author: Alessio Gusmeroli

Abstract

Polythermal glacier dynamics at Storglaciaren, Arctic Sweden, inferred using in situ geophysical techniques. Alessio Gusmeroli Submitted in June, 2010, in accordance with the requirements for the degree of PhD Swansea University, School of the Environment and Society Abstract: Geophysical experiment...

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Published: 2010
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa42751
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Abstract: Polythermal glacier dynamics at Storglaciaren, Arctic Sweden, inferred using in situ geophysical techniques. Alessio Gusmeroli Submitted in June, 2010, in accordance with the requirements for the degree of PhD Swansea University, School of the Environment and Society Abstract: Geophysical experiments were carried out to investigate spatial and temporal changes in the thermal regime and water-content of Storglaciaren, a polythermal glacier located in Arctic Sweden. Thermal changes were observed by mapping the englacial transition between permanently frozen (cold) and temperate ice with a ground-penetrating radar in April 2009. The 2009 map was compared with surveys acquired in 1989 and 2001. The comparison shows that the thinning of the cold layer observed between 1989 and 2001 is still ongoing. The thinning rate in the two time windows analyzed is approximately similar (~0.75 m/a). A volume calculation shows that the cold surface layer has lost one third of its volume in 20 years. Cross borehole zero offset radar profiles were employed to profile at high resolution, radar wave speed and power to ~100 m depth at three sites on the glacier. Radio wave speeds, interpreted in terms of ice water-content, show that water-content in the temperate ice of Storglaciaren is low (<1%) and homogeneous with depth in the upper part of the temperate ice. An increase of water-content due to strain- heating in the deepest part of the surveys (>70 m) was observed. Spatial variability due to complex interactions between water-content generated at the close-off and water-content produced by strain heating was observed at the three sites. Seismic refraction surveys were used to estimate seismic-wave attenuation using the spectral ratio method for energy travelling in the uppermost ice with an average temperature of approximately -1&deg;C. Attenuation values were derived between 100 and 300 Hz using the P-wave quality factor, Qp, the inverse of the internal friction. By assuming constant attenuation along the seismic line, mean Qp was 6+/-1. Qp varied from 8+/-1 to 5+/-1 from the near-offset to the far-offset region of the line, respectively. Since the wave progagates deeper at, far-offsets, this variation is interpreted by considering the temperature profile of the study area; far-offset arrivals sampled warmer and thus more-attenuative ice.
Keywords: Geophysics.;Geomorphology.
College: Faculty of Science and Engineering

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