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Glacier Hydraulics Explored by Means of SAR Interferometry

Eyjólfur Magnússon(1,2), Helmut Rott(1), Helgi Björnsson(2), Matthew J. Roberts(3), Finnur Pálsson(2), Halldór Geirsson(3) and Rick Bennett(4)

(1) University of Innsbruck, Innrain 52, A-6020 Innsbruck, Austria
(2) University of Iceland, Sturlugata 7 – Askja, 101 Reykjavík, Iceland
(3) Icelandic Meteorological Office, Bústadavegur 9, 105 Reykjavík, Iceland
(4) University of Arizona, Gould-Simpson Building #77, 1040 E 4th Street, AZ 85721-0077, Tucson, United States

Abstract

We analyse InSAR data from the ERS1/2 tandem mission of the glacier outlet Skeiðarárjökull in Vatnajökull, Iceland, to study vertical surface movements caused by transfer of subglacial water. We study 35 interferograms in the period from May 1995 to March 2000 from both ascending and descending orbits. In these interferograms we observe high variability in the radar line of sight (los) velocity which is predominantly caused by variability in the glacier flow, but partially related to localised water accumulation or depletion. We introduce a simple method which we use to separate the los-velocity into these two components. The study reveals area, where subglacial water accumulation and depletion is common, above the estimated subglacial course of the river Skeiðará at the most over deepened part of the glacier. There we observe between 10-30 cm/day uplift during some rainstorms and one jökulhlaup and slower subsidence (<10cm/day) following rainfall. Similar pattern is observed in data from a GPS station that was mounted at this location in the spring 2006. Our study shows that interferograms obtained subsequent to rainfall can reflect the subglacial river courses since we observe 1-5 cm/day subsidence above large part of the estimated course of the river Skeiðará in some interferograms. These observations are very relevant for advancing the knowledge on water transport in and below glaciers, a driving factor for glacier flow.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry