Master thesis defense by Falk Marius Oraschewski

Title: Modelling of firn densification in the presence of horizontal strain rates

Abstract: The densification of polar firn that is subjected to horizontal strain rates is studied. A model for the enhanced densification of the firn by strain softening is developed. Strain softening describes an acceleration of power-law creep in the presence of high horizontal strain rates, which was suggested to explain the occurrence of exceptionally thin firn in the shear margins of ice streams. With the model the effect of strain softening is compared to other strain-driven densification mechanisms, like pure shear and strain heating, and to potential variations of temperature and accumulation rate. Thereby, strain softening is identified to dominate firn densification at high strain rates. A recorded density profile along a cross-section of the North-East Greenland ice stream (NEGIS) is reproduced with the presented model with good agreement in the shear margins.

Supervisor
Aslak Grinsted

Censor
Sebastian Bjerregaard Simonsen

Participating via Zoom by using the following link: https://ucph-ku.zoom.us/j/65612060342?pwd=SkJpOHN0NjR2dWpjLzEyUTlvRHo4UT09