Modelling the surges of Vernagtferner (Ötztal Alps) since 1599

The Vernagferner in the Ötztal Alps has a history of several surges since 1599. The occurrence was periodic, with a short active advance and a much longer retreat; the whole cycle lasted, on average, 82 years. The mode of ice flow typically changed, i.e., the surge speed increased by more than one order of magnitude with heavy crevassing. The dimensions of advance and retreat were much larger than those known from other glaciers in the area (Hoinkes 1969).

In general, the understanding of surging glaciers is limited due to the sheer diversity of surge-type glaciers. Consequently, numerous mechanisms have been proposed to explain glacier surging. Here, we follow the approach by Benn et al. (2019), which includes both temperate and polythermal glacier surges, based on a coupled ice-flow and enthalpy description. The theory parameterizes key thermodynamic and hydrological processes, including surface-to-bed drainage and distributed and channelized drainage systems. The lumped-element model is extended to realistic 3D geometries and implemented within the existing enthalpy framework of the Ice-sheet and Sea-level System Model. We illustrate the surging behaviour on a simplified 3D glacier geometry and present preliminary results of the Vernagtferner.

REFERENCES

Hoinkes, H. C. (1969): Surges of the Vernagtferner in the Ötztal Alps since 1599, Canadian Journal of Earth Sciences, Vol. 6, No. 4, p. 853-861

Benn, D. I., Fowler, A. C., Hewitt, I., Sevestre, H. (2019): A general theory of glacier surges, Journal of Glaciology, Vol. 65, No. 253, p. 701-716