Master Thesis Defense by Theo Häußler

Title: Modeling Crystal Orientation Fabrics in Ice Cores and Ice - Streams: A Focus on Homogenization.

Abstract: 
Global warming puts a magnifying glass on the evolution of glacial ice around the world. The Greenland ice sheets largest dynamical feature is a fast flowing stream of ice that transports ice from far inland with a velocity of 50-500m/yr into the ocean. The mechanisms that enable the extreme properties of the North East Greenland Ice Stream (NEGIS) and how its flow regime originated is still under debate. In this thesis, we model ice crystal orientations, which have an influence on the softness of glacial ice. We constrain dynamic crystal rotation rates to measurements from ice core drilling and predict the depth averaged fabric in a survey region at the onset of the NEGIS. A spectral decomposition of the orientation density function is used to solve the local fabric problem. At scale, we solve for the coefficients of the depth averaged fabric with a finite element approach. We compare how two hypotheses modify our results, which enable us to bridge the gap between microscopic crystals and vast ice sheets. With our
experiments we examine necessary assumptions to model crystal fabrics and try to draw conclusions about the hardness and past flow of the NEGIS.

Supervisors: Nicholas Rathmann, Aslak Grinsted 
Censor: Jens Olaf Pepke Pedersen