12/31/2023 0 Comments Initial d deja vu drifterBeginning in the early 2000s, new technologies have emerged, and current methods for in situ tests include among others Doppler current profiling in supraglacial systems (e.g., Gleason et al., 2016), dye tracing (e.g., Seaberg et al., 1988 Willis et al., 1990 Fountain, 1993 Nienow et al., 1998 Hasnain et al., 2001 Schuler and Fischer, 2009), salt injection gauging (e.g., Willis et al., 2012), geophysical methods (e.g., Diez et al., 2019) and gas tracing (e.g., Chandler et al., 2013). The methods should be able to provide direct measurements of water routing on, through, and under glaciers including the water temperature, velocity, and pressure as well as the channel morphology along multiple flow paths.ĭirect measurements are the most ideal source of information but remain scarce in glacial hydrology because they are difficult to obtain (e.g., Gleason et al., 2016). Improving our understanding of glacial hydrology and its effect on glacier dynamics requires new methods. Specifically, the mechanisms driving water routing from the glacier surface to the bed remain largely unexplored. Despite these findings, major knowledge gaps remain, especially within subglacial hydrology due to limited observations of the environment. Vice versa, the velocity controls the incision rates in ice-walled channels in conjunction with water temperature and the rate of heat loss at channel boundaries ( Lock, 1990 Isenko et al., 2005 Jarosch and Gudmundsson, 2012). The channel geometry influences flow resistance and water velocity ( Germain and Moorman, 2016). These geometric adjustments often form step-pool sequences (e.g., Vatne and Irvine-Fynn, 2016) and are responsible for up to 90 % of the total flow resistance ( Curran and Wohl, 2003). The capacity of the glacial drainage system varies in both space and time and dynamically adjusts to the highly variable meltwater supply ( Schoof, 2010 Bartholomew et al., 2012). Ice-walled drainage systems have highly variable geometry, controlled by the counteracting mechanisms of melt enlargement due to dissipation of potential energy and creep closure of the viscous ice ( Röthlisberger, 1972). Water enters the englacial and subglacial drainage system through moulins, crevasses and cut-and-closure systems ( Gulley et al., 2009). Surface water is generally routed supraglacially, i.e., along the glacier surface in ice-walled drainage systems. Glacial hydrology plays a key role in glacier dynamics ( Flowers, 2018), sediment transport and its impact on fjord and proglacial ecosystems (e.g., Swift et al., 2005 Meire et al., 2017 Urbanski et al., 2017). Future deployments of drifters into englacial and subglacial channels promise new opportunities for determining hydraulic and morphologic conditions from repeated measurements of such inaccessible environments. Our results show that multimodal drifters can be a useful tool for field measurements inside supraglacial channels. Furthermore, our results indicate that prominent shapes in the sensor records are likely to be linked to variations in channel morphology and the associated flow field. Linear acceleration measurements were found to have a substantially higher variability of ☓4.4 % of the time-averaged mean magnitude, and the calculated speeds remained within ☒4.5 % of the time-averaged mean along the flow path. Magnetometer readings also exhibited low variability across deployments, maintaining readings within ☒.45 % of the time-averaged mean of the magnetometer magnitudes. The experiments ( n=55) in the supraglacial channel show that the pressure sensors consistently yielded the most accurate data, where values remained within ☐.11 % of the total pressure time-averaged mean (95 % confidence interval). To address this, we conducted repeated field experiments in a 450 m long supraglacial channel with small cylindrical drifters equipped with pressure, magnetometer, acceleration and rotation rate sensors and compared the results. Before drifters can be used as general tools in glacial studies, it is necessary to quantify the variability of their measurements. However, practical experience with drifters in glacial hydrology remains limited. Recently, sensing drifters have shown promise in river, coastal and oceanographic studies. Due to challenging field conditions, the processes driving surface processes in glacial hydrology remain sparsely studied. Surface meltwater drains through glaciers via supraglacial, englacial and subglacial systems. Glacial hydrology plays an important role in the control of glacier dynamics, of sediment transport, and of fjord and proglacial ecosystems.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |