Modelling glacier length changes in Alps on the base of tree-ring based temperature reconstructions for the last 2500 years
Mountain glaciers are well known as sensitive indicators of climate variability. In the Alps, there is a long tradition to analyse past climate evolution by reconstructing and interpreting past glacier variability. However, the knowledge beyond the last few centuries is classically obtained from field studies where materials documenting past glacier advances provide an incomplete picture: the multi-millennial Alpine glacier record is essentially an event record which documents past advance phases. It remains unclear how strong the glacier retreats between the reconstructed advances phases were, i.e. how short the glaciers were during the Roman warm period or the Medieval Climate Anomaly. Importantly, it is unknown to what extent these retreat phases can be compared to the current glacier status in the Alps.
Within this project we aim for overcoming this situation by modelling the length and volume variability of selected Alpine glaciers for the last ca. 2500 years. The model will be driven by a tree-ring based temperature reconstruction for a long summer season, i.e. May to September, which relates to the summer-temperature sensitivity of Alpine glaciers. For the temperature reconstruction, tree-ring width as well as density data will be utilized. The glacier model runs will include sensitivity test and the outputs will be compared to established Alpine glacier advance data. We will use the Open Global Glacier Model (www.oggm.org), a model accounting for glacier dynamics able to simulate past glacier advances and retreats.
The model will first be applied to selected glaciers where length data is available, and in a second step to all glaciers in the Alps. The model will be run with various ice parameters and for various time slices, allowing disentangling between stochastic and climate driven length changes. The project is part of the Doctoral programme Mountain Climate and Environment and also well embedded in the Climate Research Centre at the University of Innsbruck. It is the result of a collaboration between ACINN and the Alpine Tree-Ring Group.