[M-TT36] Cryoseismology: understanding cryospheric processes through the study of the seismic wavefield

[MTT36-P07] Tidally modulated ice fracture and calving of Langhovde Glacier in East Antarctica

*Masahiro Minowa¹, Evgeny A. Podolskiy², Shin Sugiyama^1,2 (1.Institute of Low Temperature Science, Hokkaido University, 2.Arctic Research Center, Hokkaido University)

Keywords:Ice quakes, Calving, Antarctic Ice Sheet

Iceberg calving accounts for approximately half of the ice mass loss from the Antarctic ice shelves and floating tongues. Therefore, knowing the triggering mechanisms of ice fracturing and calving is important. Glacier fracturing is a multi-temporal scale process ranging from multi-years to seconds due to glacial stress, tides, waves and hydrofracturing. We measured icequakes with a seismic array composed of three seismometers on the terminus of the ice shelf of Langhovde Glacier in East Antarctica to understand better the tidal fracturing mechanisms of ice shelves and floating tongues. Observed signals were clustered into four waveforms, and their occurrences varied with the tidal variations. Icequakes that occurred during the high tide were the most common, and they had wider frequency ranges between 15 and 100 Hz. Icequakes were also observed during the falling tides, with waveform frequencies centered at around 10 Hz. A beamforming localization suggests that the former icequakes occurred near the ice front, surface depression, and the ice shelf's base. The latter icequakes were more scattered in space, and most of them were located at the ice surface. GPS-derived ice motion was used to model stress distribution along the ice shelf. Near the terminus of the ice shelf, the tide lifted the glacier, resulting in the positive largest principal stress along the base of the glacier near the front. Our analyses highlight that the tidally modulated vertical ice motion is an important mechanism for basal ice fracturing and iceberg calving of ice shelves and floating tongues.