Simulation of the evolution of glaciers over the last 120,000 years

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Scientists have developed an unprecedented simulation that allows the last 120,000 years of glacier evolution in the Alps to be visualized in 80 seconds. This complex computer model is the result of intensive collaboration between climatologists, glaciologists and geologists.

The last Ice Age began around 115,000 years ago, and was punctuated by cold and warmer cycles, resulting in the advance and retreat of glaciers that shaped the landscape of the European Alps and their surroundings, carving out valleys in particular. A new computer model makes it possible to reconstruct this evolution with unprecedented precision. It provides a direct graphic view of the phenomena, making them accessible to a wide audience. The result of a long-term collaboration between glaciologists, climatologists and geologists from the universities of Lausanne, Bern and Zurich, the research was published in the Journal of Glaciology.

Climatology and glaciology meet

The new numerical model is unique in that, for the first time, it incorporates complex modelling of past climate, carried out by climatologists at the University of Berne.

Glaciologists then transformed this data into glacial extension by modeling ice accumulation, dynamics and melting, resulting in the most accurate simulation to date. Its unprecedented complexity makes it possible to understand the past distribution of snowfall in Alpine valleys, as well as the progression of glaciers. There are geomorphological clues in the field, such as moraines and erratic boulders, which bear witness to the past imprint of glaciers on the plains", explains Guillaume Jouvet, glaciologist at the University of Lausanne’s Faculty of Geosciences and Environment, and first author of the study. We used these traces to validate our simulation, and everything matched," he enthuses. ’ Because of the sophistication of the modeling, it took us 6 years to adjust our climate and glaciological models, and finally get the right climate and glaciers that match what we observe in reality. ’

The limits of modelling

However, the traces left in the field and acting as a gauge do not allow the model to be verified beyond 24,000 years, the period when glaciers were at their maximum.
This glacial maximum destroyed all previous evidence. Our model is therefore difficult to verify beyond 24,000 years," explains Guillaume Jouvet.

Putting global warming into perspective

The new simulation will enable us to better understand the past interaction between climate and glacier, and how our landscape was formed. As well as being of scientific interest, it provides a global context for global warming. Guillaume Jouvet comments: "The image of the different glacial cycles is quite telling. 24,000 years ago, cities such as Lausanne were covered by more than a kilometer of ice. Clearly, past cycles, caused by the Earth’s orbital variations, have nothing in common with what’s happening now, where CO2 plays an active role in melting ice. The glaciologist adds: ’What is most striking is the speed of current climate change (barely a few decades) compared with the infinitely long time span of the ice ages. ’

Scientists will now work to further improve the resolution of their model. It is not yet fine enough to reproduce the complex topography of the high mountains, and this is likely to cause an overestimation of the ice cover. We have just started a new project using artificial intelligence to speed up our models and achieve the necessary 200m resolution," explains Guillaume Jouvet.

Reference :

G. Jouvet, D. Cohen,, E. Russo, J. Buzan , C. C. Raible , W. Haeberli , S. Kamleitner , S. Ivy-Ochs, M. A. Imhof , J. K. Becker , A. Landgraf and U. H. Fischer, Coupled climate-glacier modelling of the last glaciation in the Alps, Journal of Glaciology.