Large-scale investigation into iceberg-tsunamis generated by various iceberg calving mechanisms

© 2020 Elsevier B.V. Mass balance analysis of ice sheets is a key component to understand the effects of global warming with iceberg calving as a significant contributor. Calving recently generated tsunamis of up to 50 m in amplitude endangering human beings and coastal infrastructure. Such iceberg-tsunamis (IBTs) have been investigated based on 66 unique large-scale experiments conducted in a 50 m × 50 m large basin at constant water depth h. The experiments involved five iceberg calving mechanisms: A: capsizing, B: gravity-dominated fall, C: buoyancy-dominated fall, D: gravity-dominated overturning and E: buoyancy-dominated overturning. The kinematics of the up to 187 kg heavy plastic blocks mimicking icebergs was measured with a motion sensor and the wave profiles were recorded with wave probes at up to 35 locations. The IBTs from the gravity-dominated mechanisms (B and D) are roughly an order of magnitude larger than from mechanisms A, C and E. Empirical equations for preliminary hazard assessment and mitigation for the maximum wave height, amplitude and period for both the near- and far-field are derived for the five calving mechanisms individually and combined. The relative released energy, Froude number and relative iceberg width are the most influential dimensionless parameters in these equations. A maximum wave height decay trend close to (r/h)−1.0 is observed, with r as the radial distance, in agreement with the theoretical wave decay from a point source. The empirical equations are applied to a past event resulting in a good agreement and the upscaled wave periods to typical Greenlandic conditions overlap with the lower spectrum of landslide-tsunamis. However, empirical equations for landslide-tsunamis were found to be of limited use to predict IBTs in the far-field supporting the need of the newly introduced empirical equations for IBT hazard assessment and mitigation