Insights Into Helheim Glacier Terminus Dynamics Through Integration of Two Autonomous Terrestrial LiDAR Scanners, 2015 – 2019

Abstract:

Iceberg calving is an important component of mass loss, accounting for roughly one half of ablation from the Greenland Ice Sheet. The question of whether calving triggers acceleration or whether acceleration causes an increase in calving is difficult to answer in part by a lack of long-term, high-resolution, datasets of ice dynamics. To fill this gap, we installed two autonomous terrestrial laser scanners (ATLAS) near the terminus of Helheim Glacier in 2015 and 2018 on the south and north sides of Helheim Fjord, respectively. Each ATLAS system scans every 6 hours except in the winter when scans are obtained once per day; together, the ATLAS systems provide complete coverage of Helheim Glacier’s terminus.

Here, we generate time series of ice velocity, height above buoyancy, tidal admittance, and strain rate to observe ice dynamic responses or lack thereof to calving events at the terminus from 2015 -2019. From tidal admittance amplitude and phase lag we can determine the magnitude of tidal forcing on ice velocity and changes in basal conditions. The length of our time series allows us to observe hourly to seasonal timescales of velocity variations and terminus perturbations. Preliminary results show a non-linear velocity response to calving events at Helheim Glacier, which is similar to previous studies at Jakobshavn Isbrae. Our observations provide a unique insight on the controls of mass flux near the terminus of Helheim Glacier which will help elucidate the mechanisms that govern glacier stability.