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The Water Cycle
Published in Aurèle Parriaux, Geology, 2018
All glaciers have two distinct parts (Fig. 7.44): Accumulation zone: The upper part where snow deposits are more abundant than losses from melting and sublimation. In valley glaciers, these are often large plateaus and the beginning of the tongue.Ablation zone: The lower part of the glacier where losses exceed snowfall deposits. They are the lower part of the tongue of valley glaciers.
The Water Cycle
Published in Aurèle Parriaux, Geology, 2018
All glaciers have two distinct areas (Fig. 7.45): Accumulation zone: The upper part where snow deposits are more abundant than losses from melting and sublimation. In valley glaciers, these are often large plateaus and the beginning of the tongue.Ablation zone: The lower part of the glacier where losses exceed snowfall deposits. They are the lower part of the tongue of valley glaciers.
Spatiotemporal variations in surface albedo during the ablation season and linkages with the annual mass balance on Muz Taw Glacier, Altai Mountains
Published in International Journal of Digital Earth, 2022
Xiaoying Yue, Zhongqin Li, Feiteng Wang, Jun Zhao, Huilin Li, Changbin Bai
To evaluate the accuracy of Landsat-retrieved albedo, we compared the hourly AWS-measured values at the time of Landsat overpasses with the retrieved values from Landsat at the pixel where the AWS was installed (Table 3). The differences in albedo obtained by the two observation methods ranged from −0.07 to +0.03, with the mean absolute difference of 0.03. The root mean square error (RMSE) was 0.04. In addition to errors related to the retrieval method, the input data, and the environmental factors (Klok, Greull, and Oerlemans 2003; Fugazza et al. 2016; Yue et al. 2017; Naegeli et al. 2019), error was most likely to stem from the different spatial resolutions. The AWS monitored a theoretical footprint of approximately 300 m2, while the pixel area of the Landsat satellite is 900 m2. Because the AWS was installed in the upper ablation zone of the glacier, the glacier surface is usually heterogeneous. Cryoconite has been observed in the instrument footprint during field visits, as well as melt channels and small meltwater ponds offsetting the spectral properties of the surface compared with the spectral response of snow and ice, inducing errors in the comparison between in situ and Landsat-retrieved albedo.
Glacial burst triggered by triangular wedge collapse: a study from Trisul Mountain near Ronti glacier valley
Published in Geomatics, Natural Hazards and Risk, 2022
Sandeep Kumar Mondal, Rishikesh Bharti
Ronti glacier falls in the category of the hanging glacier that lies adjacent to Nanda Gunti (6390 m asl) to its east and Trisul (7120 m asl) to its west. It is a northward-flowing glacial body with the main trunk (∼6 km long) and three connecting flanges accounting for a total area of about 11.8 sq. km. The snout of the Ronti glacier lies at an elevation of ∼4100 m asl, with its ablation zone characterized by crescentic crevasses, discernible traverse, fine-textured debris, and supraglacial lakes with an area of not more than 500 sq. m. Studies conducted using topographic maps and satellite datasets have suggested that two different categories of the moraine cover the glacier. One is vegetation-covered (conifer, juniper, birch, etc.) older moraine, mainly observed below ∼3000 m asl and characterized by the rolling crest. Another is non-vegetated or poorly vegetated fresh moraine, followed until the glacier’s snout and characterized by a sharp ridge (Rana et al. 2021). Down the valley, where the older moraine culminates, the morphology of the valley is steeper, and the river flows through the gorge with large boulders. The study area falls within the Alaknanda catchment on the north-eastern slope of Trisul mountain, standing beside the valley of the Ronti glacier (Figure 1).
Rock fracturing by subglacial hydraulic jacking in basement rocks, eastern Sweden: the role of beam failure
Published in GFF, 2021
Maarten Krabbendam, Romesh Palamakumbura, Christian Arnhardt, Adrian Hall
Potential groundwater overpressure conditions in the bedrock below Forsmark have been studied and discussed extensively (e.g., Talbot 1990, 1999, 2014; Hökmark et al. 2010; Lönnqvist & Hökmark 2013; Hökmark & Lönnqvist 2014). The normal hydraulic gradient of a sloping ice front (e.g., Boulton et al. 1993) may lead to overpressure in a marginal or proglacial setting, in particular if the water is “locked up” below a low conductivity layer, like permafrost. However, no strong water pressure fluctuations are expected from these mechanisms. In contrast, in the ablation zone of the western Greenland Ice Sheet pressure measurements in boreholes (with ice thickness between 150–800 m) have shown strongly fluctuating water pressures on a seasonal and daily basis at the ice-bed interface (Andrews et al. 2014; Claesson Liljedahl et al. 2016; Wright et al. 2016; Harper et al. 2019). Water pressures in boreholes varies from 80 to 110% of overburden pressure. In moulins, in regions that are well-connected to the bed, Andrews et al. (2014) measured water-pressure fluctuations between 60 and near 100% overburden pressure on a daily basis during the melt season.