Abstract
AbstractWe reconstruct englacial and subglacial drainage at Skálafellsjökull, Iceland, using ground penetrating radar (GPR) common offset surveys, borehole studies and Glacsweb probe data. We find that englacial water is not stored within the glacier (water content ~0–0.3%). Instead, the glacier is mostly impermeable and meltwater is able to pass quickly through the main body of the glacier via crevasses and moulins. Once at the glacier bed, water is stored within a thin (1 m) layer of debris‐rich basal ice (2% water content) and the till. The hydraulic potential mapped across the survey area indicates that when water pressures are high (most of the year), water flows parallel to the margin, and emerges 3 km down glacier at an outlet tongue. GPR data indicates that these flow pathways may have formed a series of braided channels. We show that this glacier has a very low water‐storage capacity, but an efficient englacial drainage network for transferring water to the glacier bed and, therefore, it has the potential to respond rapidly to changes in melt‐water inputs. © 2015 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.
Highlights
The glacial hydrological system modulates ice dynamics and is, a vital component in understanding how glaciers respond to climate change (Mair et al, 2002; Copland et al, 2003; Clarke, 2005)
Using ground penetrating radar (GPR), field observations and instrumentation, this study has determined the internal structure of the glacier, and we present a hydrological model of Skálafellsjökull
The main glacier body has a very low water content and the base consists of a thin debris-rich basal ice layer with a 2% water content
Summary
The glacial hydrological system modulates ice dynamics and is, a vital component in understanding how glaciers respond to climate change (Mair et al, 2002; Copland et al, 2003; Clarke, 2005). ENGLACIAL AND SUBGLACIAL WATER FLOW AT SKÁLAFELLSJÖKULL, ICELAND calculate the composition of ice, air, water and debris within the glacier, as well as calculate the reflectivity of the bed We use these data, in combination with borehole observations and in situ subglacial instrumentation and theoretical drainage reconstructions to reconstruct the glacier’s hydrological system. Numerous researchers (Winebrenner et al, 2003; MacGregor et al, 2007; Matsuoka et al, 2010; Jacobel et al, 2009, 2010) have shown that the power of electromagnetic energy returned from the subglacial interface is determined by three factors: the dielectric properties of the reflector (the basal reflectivity) (R), losses due to geometric spreading (which are related to glacier depth), and losses due to dielectric attenuation within the ice (La) These factors are represented as: Pr. Most researchers take the log of both sides of Equation (11) and calculate one-way attenuation rate Na, which is related to La by: Na. Dielectric attenuation, which is primarily a function of ice temperature and impurity content, can be calculated using three methods:. Power (Pr) values are obtained by summing the squared amplitude under the bed echo wavelet (Gades et al, 2000): Pr Pro h20 h2 exp
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