Pressure and inertia sensing drifters for glacial hydrology flow path measurements

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.

Multi-Species Assessment of Injury, Mortality, and Physical Conditions during Downstream Passage through a Large Archimedes Hydrodynamic Screw (Albert Canal, Belgium)

“…The coordinate transformation has no impact on the resulting analysis, but does aid in the interpretation of the sensor data results, because the accelerometer data can be viewed from a fixed inertial reference frame. Afterwards, we estimated the change in the three-dimensional velocity over time by integrating the linear acceleration data, as in [39]. Changes in the rotational velocity were obtained directly by calculating the difference between subsequent angular velocity measurements recorded by the rate gyro.…”

Subsurface Flow Path Modeling From Inertial Measurement Unit Sensor Data Using Infinite Hidden Markov Models

“…1) Data used for reconstruction: All data collection was done using identical Lagrangian drifters. The detailed overview of the devices is given in [20]. Each example data consists of 9dof IMU (BNO055, Bosch Sensortec, Germany) time series recordings.…”

“…The GNSS surface drifters give a global reference (latitude,longitude) that was used as ground truth. More detailed overview of the glacial channel data collection can be found in [15], [20].…”

Characterising englacial R-channels using artificial moulins

“…Fountain and others, 2005; Church and others, 2019). Current developments include measurement techniques such as the Cryoegg (Prior-Jones and others, 2021), the Glacsweb wireless probe (Hart and others, 2019) or drifters (Alexander and others, 2020) that can be deployed into glacier streams to take in situ measurements. In addition to these in situ measurement techniques, remote geophysical methods have been used to infer properties of glacier drainage systems by radar and seismic imaging (e.g.…”