Estimation of Ice Volume from Field Data and the Shallow Ice Approximation Model: A Case Study of Satopanth Glacier, Central Himalaya, India

The estimation of ice volume is crucial for assessing water reserves stored in the glaciers. Such estimates, based on field measurements, are very rare in high mountain Himalaya. Ice volume estimations are mainly based on the remote sensing techniques and scaling laws. There large uncertainties in these estimates. Direct measurements of the entire bedrock using ground penetrating radars (GPR), in debris covered glaciers are very difficult. In this work, we present a method based on GPR and differential global positioning system (DGPS) surveys.

We have estimated the volume of ablation zone of the debris covered Satopanth glacier (SPG), Central Himalaya. We have used field data on the surface topography and surface velocities from field measurements, in the period 2014-2018, using DGPS observations, data of the ice depth at three locations using GPR. We have analysed this data in the framework of the shallow ice approximation (SIA) to estimate the ice depth profile and the volume. The three GPR profiles were used to estimate the flow parameters considering the nearby surface velocities. In this way, we have calculated deformation (f_d) and slip (f_s) parameters to be 3.46 × 10^-24 Pa^-3 S^-1 and 2.28 × 10^-20 Pa^-3 m² S^-1 respectively. We have assumed these values to be constant throughout the glacier. Further, assuming a parabolic bedrock, we have used the above estimate of the flow parameters, other data and the SIA to calculate the depth profile, cross-section area profile and the ice volume. We have thus estimated the volume in the ablation zone of the glacier to be 0.69 km³. Our method can be useful to estimate the ice volume of other debris covered glaciers and for the validation of the estimates based on remote sensing data.