Multi-method observation and analysis of a tsunami caused by glacier calving

Martin P Lüthi,Andreas Vieli

doi:10.5194/tc-10-995-2016

Abstract

Abstract. Glacier calving can cause violent tsunami waves which, upon landfall, can cause severe destruction. Here we present data acquired during a calving event from Eqip Sermia, an ocean-terminating glacier in west Greenland. During an exceptionally well-documented event, the collapse of 9 × 105 m3 ice from a 200 m high ice cliff caused a tsunami wave of 50 m height, traveling at a speed of 25–33 m s−1. This wave was filmed from a tour boat at 800 m distance from the calving face, and simultaneously measured with a terrestrial radar interferometer and a tide gauge. Tsunami wave run-up height on the steep opposite shore at a distance of 4 km was 10–15 m, destroying infrastructure and eroding old vegetation. These observations indicate that such high tsunami waves are a recent phenomenon in the history of this glacier. Analysis of the data shows that only moderately bigger tsunami waves are to be expected in the future, even under rather extreme scenarios.

Highlights

Subaerial mass movement into water, such as landslides, pyroclastic flows, and glacier calving, produce tsunami waves that travel for long distances, producing high wave runups on shorelines, and causing disasters far away from the generation area (e.g., Walder et al, 2003; Fritz et al, 2003)
The elevations derived in this way differ from the Greenland Ice Mapping Project (GIMP) digital elevation model (GIMPDEM; Howat et al, 2014) on stable terrain by less than 5 m on slightly inclined areas, but can exceed 20 m on steep terrain
The exact position of the boat was determined by analysis of the terrestrial radar interferometer (TRI) intensity data on which the boat is clearly visible as a bright spot which moves against the ocean currents

Summary

Introduction

Subaerial mass movement into water, such as landslides, pyroclastic flows, and glacier calving, produce tsunami waves that travel for long distances, producing high wave runups on shorelines, and causing disasters far away from the generation area (e.g., Walder et al, 2003; Fritz et al, 2003). As well as rotating icebergs in fjords, can trigger large tsunami waves which have the potential to threaten lives and cause damage on the coasts (e.g., MacAyeal et al, 2011; Levermann, 2011). Wave heights can still far exceed 1 m at 3 km distance, with dominant periods of 30–60 s (Amundson et al, 2010, and unpublished pressure sensor data from different locations in the Kangia ice fjord). Such calving waves cause lowfrequency seismicity that is detectable at up to 150 km distance (Amundson et al, 2012; Walter et al, 2012, 2013). Calving-induced seismicity from full-thickness calving has even been observed on the global seismic network as slow seismic events, sometimes termed “glacial earthquakes” (Ekström et al, 2003, 2006; Amundson et al, 2008; Nettles et al, 2008)

Methods

Results

Discussion

Conclusion