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Universität Tübingen

1. Eichler, Jan. Chemical Impurities and Physical Properties of Polar Ice .

Degree: 2019, Universität Tübingen

The Greenland Ice Sheet and the Antarctic Ice Sheet are the largest reservoirs of freshwater on our planet. They consist of ice which formed over thousands of years out of the precipitation and due to natural densification of snow. As such, polar ice represents a unique archive of the past climate. The large ice masses flow under their own weight causing a transport of ice from the inlands towards the oceans. Numerical flow models are used to simulate the ice dynamics, i. a., in order to project future contributions of the ice sheets to the rising sea level. The viscoplastic deformation of ice on the micro-scale involves similar mechanisms as the deformation of other poly-crystalline materials. The shear of individual crystals is accompanied by recrystallization and the development of characteristic microstructures. Thus, structural-geological concepts and methods can be applied to natural ice samples in order to study their deformation state and active physical processes. Chemical impurities are deposited in snow and ice during the precipitation and reflect the aerosol composition of the atmosphere. As such they play an important role for the reconstructions of the climate of the past. Despite their extremely low concentrations, impurities influence many physical properties of ice, in particular also the deformation rate. The concentrations of the different impurities vary with depth and these variations are correlated with heterogeneities in the flow-velocity profile. This results in the development of localized shear zones in ice. A better understanding of the mechanisms is necessary in order to implement the effect of impurities into the flow models. The presented thesis addresses the relationship between the chemical impurities and the physical properties of polar ice. A central challenge of the project is to understand in which form impurities integrate in ice and where they are located in the bulk, respectively how they interact with it during deformation and recrystallization. A combination of methods for the microstructural analysis was applied to natural ice material from ice cores. The distribution and composition of impurities was analyzed using a confocal cryo-Raman microscope. Within the scope of this thesis, new routines for the acquisition and data processing were developed. The results reveal a complex interplay between impurities, crystal structure and localized deformation in ice. On the one hand, high impurity concentrations cause higher strain rates occurring together with small grain sizes. On the other hand, the deforming ice matrix affects the distribution of impurities and possibly also their chemical composition. The portion of dissociated components in ice could be estimated only qualitatively and through the comparison to the chemical analysis of the meltwater. However, the Raman-spectroscopy data clearly suggest that microscopic inclusions of second phase are present in solid ice in significantly higher concentrations, compared to liquid water. Mixing and… Advisors/Committee Members: Weikusat, Ilka (Jun.-Prof. Dr.) (advisor).

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Eichler, J. (2019). Chemical Impurities and Physical Properties of Polar Ice . (Thesis). Universität Tübingen. Retrieved from http://hdl.handle.net/10900/91259

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Eichler, Jan. “Chemical Impurities and Physical Properties of Polar Ice .” 2019. Thesis, Universität Tübingen. Accessed September 21, 2019. http://hdl.handle.net/10900/91259.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Eichler, Jan. “Chemical Impurities and Physical Properties of Polar Ice .” 2019. Web. 21 Sep 2019.

Vancouver:

Eichler J. Chemical Impurities and Physical Properties of Polar Ice . [Internet] [Thesis]. Universität Tübingen; 2019. [cited 2019 Sep 21]. Available from: http://hdl.handle.net/10900/91259.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Eichler J. Chemical Impurities and Physical Properties of Polar Ice . [Thesis]. Universität Tübingen; 2019. Available from: http://hdl.handle.net/10900/91259

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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