Johan Gaume, EPFL expert in avalanches and geomechanics, turned to ice. Its objective is to better understand the correlation between the size of an iceberg and the amplitude of the tsunami that results from its calving. Gaume, along with a team of scientists from other research institutes, has just unveiled a new method for modeling these events. Their work appears in Earth & Environment Communications, a new journal from Nature Research.
These scientists are the first to simulate the phenomena of glacier fracture and wave formation when the iceberg falls into the water. “Our goal was to model the explicit interaction between water and ice – but this has a significant cost in computational time. So we decided to use a continuum model, which is very powerful numerically and which gives results both conclusive and consistent with a large part of the experimental data, ”explains Gaume, who heads the Snow Avalanche Simulation Laboratory (SLAB) at EPFL and is the corresponding author of the study. involved in the study are the University of Pennsylvania, the University of Zurich, the University of Nottingham and the WSL Swiss Institute for Snow and Avalanche Research.
Improve calving laws
The scientists’ method can also shed light on the specific mechanisms involved in glacial rupture. “Researchers can use the results of our simulations to refine the calving laws incorporated into their large-scale models to predict sea level rise, while providing detailed information on the size of icebergs, which represent a quantity significant loss of mass “, explains Gaume. .
Calving occurs when pieces of ice at the edge of a glacier break off and fall into the sea. The mechanisms causing the breakage usually depend on the height of the water. If the water level is low, the iceberg detaches from the top of the glacier. If the water level is high, the iceberg is longer and comes off the bottom, before finally floating to the surface due to buoyancy. These different mechanisms create icebergs of different sizes – and therefore waves of different amplitudes. “Another event that can trigger a tsunami is the change in an iceberg’s center of gravity, causing the iceberg itself to rotate,” Gaume explains. “We were able to simulate all of these processes.”
In Greenland, scientists placed a series of sensors at Eqip Sermia, a 3 km-wide outlet glacier from the Greenland ice cap that ends in a fjord with a 200m ice cliff. In 2014, an iceberg measuring about 1 million m3 (the equivalent of 300 Olympic swimming pools) broke off the glacier front and produced a tsunami 50 m high; the wave was still 3 m high when it reached the first populated shore some 4 km away. The scientists tested their modeling method on large-scale field datasets from Eqip Sermia as well as empirical data on tsunami waves obtained in a laboratory basin at the Deltares Institute in the Netherlands.
Projects in the pipeline
Melting glaciers have become a major area of research today due to global warming. One of the scientists from the University of Zurich involved in the study this year launched a new research project with funding from the Swiss National Science Foundation. This project will study the dynamics of Greenland’s fastest glacier, Jakobshavn Isbrae, by combining data from individual field experiments in Greenland with the results of simulations run using the SLAB model. “Our method will also be used to model chains of complex processes triggered by gravitational mass movements, such as the interaction between an avalanche of rocks and a mountain lake,” explains Gaume.
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