Dynamics and GPR stratigraphy of a polar rock glacier on James Ross Island, Antarctic Peninsula

Abstract

ABSTRACT. We describe field measurements (ground-penetrating radar (GPR), geodetic survey and ice-core drilling) to provide new information on the movement mechanism and internal structure of a polar rock glacier on James Ross Island, Antarctic Peninsula. We collected GPR data along longitudinal and transverse profiles. The longitudinal GPR profiles identify inter-bedded debris-rich layers that dip up-glacier, similar to the thrust structures in the compression zone of a valley glacier. The transverse GPR profiles indicate a syncline structure inclined towards the central part of the rock glacier, resembling the transverse foliation of a valley glacier. The stratigraphy of two boreholes shows that the rock glacier consists primarily of bubbly ice with thin debris-rich layers, an internal structure similar to the 'nested spoons' structure common in the interior of valley glaciers. These results indicate that the glacier motion is controlled by shear movement, common in valley glaciers. The geodetic survey confirms that flow velocities decrease towards the lower part of the rock glacier. Such heterogeneous movement causes longitudinal compression and forms thrusts which then create the debris-rich layer by uplifting basal ice and debris. Pushing of the upstream ice against the downstream ice bends the surface layers, forming transverse ridges on the rock glacier surface.

Development of tongue-shaped and multilobate rock glaciers in alpine environments – Interpretations from ground penetrating radar surveys

“…Rock glaciers are creeping permafrost bodies for which the material properties are best known from inspection of outcrops (Barsch, 1996), a limited number of drill corings (Vonder Mühll and Holub, 1992;Haeberli and Vonder Mühll, 1996;Arenson et al, 2002), and various geophysical investigations in Norway (Berthling et al, 2000;Isaksen et al, 2000;Berthling et al, 2003;Sollid and Christiansen, 2003), Antarctica (Fukui et al, 2007(Fukui et al, , 2008, the European Alps (Haeberli et al, 1982;Haeberli, 1985;Hoelzle, 1993;Wagner, 1996;Vonder Mühll, 1996;Monnier et al, 2008), Swiss Alps (Delaloye and Lambiel, 2005;Otto and Sass, 2006), and the United States (Degenhardt et al, 2000;Degenhardt et al, 2008). Given these investigations, much remains to be learned with regard to composition and structure of alpine permafrost rock glaciers.…”

“…This type of structure is significantly different than the "nested spoons" structure that was interpreted for the Tumbledown Norte rock glacier on James Ross Island, Antarctic Peninsula by Fukui et al (2008). Their results, which were based on stratigraphic analyses of GPR surveys and analysis of ice core samples, showed that despite its talus-derived appearance (e.g., prominent ridge and furrow surface morphology), the internal structure of the rock glacier is similar to that of valley glaciers and its motion is controlled by shear.…”

Helicopter-borne transient electromagnetics in high-latitude environments: An application in the McMurdo Dry Valleys, Antarctica

“…Low-frequency radar (10-100 MHz) is commonly used to measure the basal topography of glaciers (e.g., Berthling et al, 2000;Isaksen et al, 2000;Degenhardt and Giardino, 2003;Hubbard et al, 2004;Engel et al, 2012), whereas a shorter wavelength (100-400 MHz) is used when high resolution is required (e.g., Fukui et al, 2008;Sold et al, 2014). Because the speed of EM waves in ice is in the range of 0.167-0.169 m:ns −1 , (which adds some uncertainties depending on the value chosen), the vertical resolution (about a quarter of the radar wavelength) ranges from approximately 4 m at 10 MHz to 0.1 m at 400 MHz.…”

Periglacial features in Patriot Hills, Ellsworth Mountains, Antarctica

“…Rock glaciers have been identified in some areas of the coast and in subantarctic islands (Mayewski, 1979;Mayewski and Hassinger, 1980;Hassinger and Mayewski, 1983;Serrano and López-Martínez, 2000;Fukui et al, 2008), in the Transantarctic Mountains (Bockheim, 1995) and in some sectors of the McMurdo Dry Valleys (Rignot et al, 2002;McLeod et al, 2008;Shean and Marchant, 2010).…”