New ground penetrating radar (GPR) observations on the Múlajökull surge-type outlet glacier, cen... more New ground penetrating radar (GPR) observations on the Múlajökull surge-type outlet glacier, central Iceland, are presented. Overall 10.5 km of GPR profile lines were recorded parallel to the glacier margin in August, 2015. Detailed GPR investigations combined with high-accuracy GPS measurements allowed to build a high-resolution model of the subglacial topography. We provide new evidence of streamlined ridges beneath Múlajökull’s marginal zone interpreted as drumlins and show the location of the upper edge of the drumlin field. This discovery improves understanding of the location, morphology and development of drumlins as other geophysical observations of subglacial bedforms beneath modern outlet glaciers are quite rare. The location of drumlins corresponds with the position of the major sets of crevasses in the digital elevation model (2008) suggesting the presence of additional drumlins beneath such crevasses in the ice-marginal zone. We suggest this semi-circular pattern of crevasses to be formed due to the variable glacier strain rates created by the subglacial topography. Numerous hyperbolic diffractions representing reflections of englacial channels are found in radar profiles suggesting a well-developed channelized drainage system of a surge-type glacier in its quiescence phase. The calculated thinning of the ice surface in the investigated area (0. 65 km2) is on 23 average 17.9 m during 2008–2015.
This work describes preliminary results obtained during the expedition to Múlajökull and Þjórsárj... more This work describes preliminary results obtained during the expedition to Múlajökull and Þjórsárjökull glaciers in August, 2014. In the research ground penetrating radar (GPR) Zond 12-e was used. GPR measurements were performed on both outlet glaciers using 38 MHz and 75 MHz antenna systems. During data acquisition 2000 ns time window was used, while length of profiles was determined using GPS device Garmin GPS-76. In total approximately 3 km of GPR profiles were recorded. GPR signals propagation speed in glacier ice was determined using reflections from internal meltwater channels of glacier. In obtained radarogramms it was possible to trace reflections from the glacier bed till depth of approximately 144 m as well as numerous prominent reflections from internal meltwater channels of glacier. In one of the obtained radarogramms possible subglacial channel below Múlajökull glacier was identified. Also feature of subglacial topography that resembles drumlin was identified. The area of abundant infiltrated water was distinguished close to the ice margin in the radarogramm obtained on Þjórsárjökull suggesting successive supraglacial meltwater infiltration towards glacier margin.
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Papers by Davids Berzins
the location of the upper edge of the drumlin field. This discovery improves understanding of the location, morphology and development of drumlins as other geophysical observations of subglacial bedforms beneath modern outlet glaciers are quite rare. The location of drumlins corresponds with the position of the major sets of crevasses in the digital elevation model (2008) suggesting the presence of additional drumlins beneath such crevasses in the ice-marginal zone. We suggest this semi-circular pattern of crevasses to be formed due to the variable glacier strain rates created by the subglacial topography. Numerous hyperbolic diffractions representing reflections of englacial channels are found in radar profiles suggesting a well-developed channelized drainage system of a surge-type glacier in its quiescence phase. The calculated thinning of the ice surface in the investigated area (0. 65 km2) is on 23
average 17.9 m during 2008–2015.