Around 115,000 years ago, the last glacial period in the earth’s history began. It was an eventful time, as glaciers advanced from the Alps onto the Swiss Plateau, retreated, and then advanced again. In the process, the powerful ice flows carved out valleys, such as the Rhône Valley, bringing rock debris — ranging in size from fine sediment to boulders weighing several tonnes — across the landscape with them. This debris, deposited as moraines, formed the lush, green foothills of the Alps. The heavy boulders, known as erratics, can be found spread out across the Swiss Plateau, in Alpine valleys and in the Jura Mountains.
Three hundred years of glacial history research
Despite the fact that explorers and scientists have been researching the glacial history of the Alps for almost 300 years, no one has previously succeeded in unequivocally identifying which climate developments led to large-scale glaciation
. Questions remained about what conditions affected how the glaciers expanded, how thick the ice was, how often the ice sheet expanded and retreated, and what caused the ice to expand at different rates in different Alpine regions.
To gain a better understanding of all this, Julien Seguinot from ETH Zurich’s Laboratory of Hydraulics, Hydrology and Glaciology, together with several colleagues, simulated glacier development in the Alps over the last 120,000 years on the CSCS supercomputer “Piz Daint”. Their study was recently published in the journal
The Cryosphere
.
To simulate ice build-up and glacier spread, they used a special model (Parallel Ice Sheet Model, or PISM) that they fed with data about the initial topography of mountain ranges and glaciers, the physical properties of rock and glaciers based partly on observations from the Antarctic and Greenland, heat flow from the earth’s interior, and the climatic conditions. They based the latter on present-day weather data combined with paleo-climate records deduced from sediment and ice cores from the last 120,000 years.
