Abstract
Abstract. Glacial hydrology plays an important role in the control of glacier dynamics, of sediment transport, and of fjord and proglacial ecosystems. Surface meltwater drains through glaciers via supraglacial, englacial and subglacial systems. Due to challenging field conditions, the processes driving surface processes in glacial hydrology remain sparsely studied. Recently, sensing drifters have shown promise in river, coastal and oceanographic studies. However, practical experience with drifters in glacial hydrology remains limited. Before drifters can be used as general tools in glacial studies, it is necessary to quantify the variability of their measurements. 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. The experiments (n=55) in the supraglacial channel show that the pressure sensors consistently yielded the most accurate data, where values remained within ±0.11 % of the total pressure time-averaged mean (95 % confidence interval). Magnetometer readings also exhibited low variability across deployments, maintaining readings within ±2.45 % of the time-averaged mean of the magnetometer magnitudes. Linear acceleration measurements were found to have a substantially higher variability of ±34.4 % of the time-averaged mean magnitude, and the calculated speeds remained within ±24.5 % of the time-averaged mean along the flow path. 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. Our results show that multimodal drifters can be a useful tool for field measurements inside supraglacial channels. 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.
Highlights
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)
This calculation resulted in unrealistically high required sample sizes (Table ). These high numbers are composed of several components: one part is caused by the sensor accuracy and technical problems causing high variations in the measured data, and the second part of the inaccuracy is due to spatial and temporal flow variability between deployments and along the flow path
The multimodal drifter platform tested in this work measures the total water pressure, linear acceleration, magnetic field strength and rotation rate while flowing along a glacial channel
Summary
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). 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). Despite these findings, major knowledge gaps remain, especially within subglacial hydrology due to limited observations of the environment. 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
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