Glacier–volcano interactions deduced by SAR interferometry

Abstract

Glacier-surface displacements produced by geothermal and volcanic activity beneath Vatnajökull ice cap in Iceland are described by field surveys of the surface topography combined with interferograms acquired from repeat-pass synthetic aperture radar images. A simple ice-flow model serves well to confirm the basic interpretation of the observations. The observations cover the period October 1996–January 1999 and comprise: (a) the ice-flow field during the infilling of the depressions created by the subglacial Gjálp eruption of October 1996, (b) the extent and displacement of the floating ice cover of the subglacier lakes of Grímsvötn and the Skaftá cauldrons, (c) surface displacements above the subglacier pathways of the jökulhlaups from the Gjálp eruption site and the Grímsvötn lake, (d) detection of areas of increased basal sliding due to lubrication by water, and (e) detection of spots of temporal displacement that may be related to altering subglacial volcanic activity. At the depression created by the Gjálp eruption, the maximum surface displacement rate away from the radar decreased from 27 cm d−1 to 2 cm d−1 over the period January 1997–January 1999. The observed vertical displacement of the ice cover of Grímsvötn changed from an uplift rate of 50 cm d−1 to sinking of 48 cm d−1, and for Skaftá cauldrons from 2 cm d to 25 cm d−1.

Remote sensing of glacier- and permafrost-related hazards in high mountains: an overview

“…(Björnsson et al, 2001), (cf. Haeberli, 1983;Walder and Driedger, 1995) (1.4) Breaching of thermokarst and supraglacial lakes On ice-rich permafrost or stagnant glacier ice.…”

“…Björnsson et al, 2001). However, strictly speaking this technique does track three-dimensional terrain surface shifts rather than elevation changes at fixed positions.…”

“…Ice cover on volcanoes and its changes (and partially also volcanic activity) can be monitored by remote sensing (see 2) (Björnsson et al, 2001;Dean et al, 2004;Julio Miranda et al, 2005) ( Monitoring of permafrost deformation by repeat high-resolution optical remote sensing and DInSAR. (Kääb, 2000;Kääb, 2002;Kenyi and Kaufmann, 2003;Strozzi et al, 2004), (Figs.…”

Glacier shrinkage and negative mass balance in the Chilean Lake District (40°S) / Rétrécissement glaciaire et bilan massique négatif dans la Région des Lacs du Chili (40°S)

“…In Iceland, for instance, where active volcanoes are closely related to glacial activity, it has been shown that both geological and geo-environmental systems have strong relationships (Sigmundsson, 1991;Sigvaldason, 2000;Björnsson et al, 2001;Maclennan et al, 2002). At a small time scale, active geothermal systems at ice-capped volcanoes can enhance icemelt, especially at the base of glaciers (Björnsson, 1998), sometimes generating catastrophic floods associated with eruptions, that are known as jökulhlaups (Matthews & Clague, 1993), and also the main type of lahars produced in southern Chile (Moreno, 1993;Naranjo & Moreno, 2004).…”

Discharge and suspended sediment dynamics during two jökulhlaups in the Skaftá river, Iceland

“…Vatnajökull overlies part of the eastern volcanic zone, encompassing the large volcanoes Hamarinn, Bárdarbunga and Grímsvötn (Björnsson and Einarsson, 1990). As part of the Grímsvötn field, the Skaftá basin is geothermally influenced and seismically active (Björnsson, 1977(Björnsson, , 1988(Björnsson, , 2002Björnsson et al, 2001;Björnsson and Einarsson, 1990).…”