| dc.description.abstract | This thesis provides a comprehensive study of the controls on grain growth, specifically in the North Greenland
Eemian Ice Drilling (NEEM) ice core. It is very important to understand which processes control the grain size
in polar ice, because grain size can influence the strength of the ice structure and the deformation mechanisms
in the ice sheets. These processes in turn effect the behaviour and movement of the massive ice sheets that
have a large impact on global climate and sea level. The controls on grain size in the ice sheets can vary with
depth, age, impurity content, temperature and stress, and the relations between these various processes are not
yet completely understood. To improve the understanding of grain growth relations, one of the main aims of
this thesis is to see whether the gradual increase of grain-size at the deepest glacial deposits in the NEEM ice
core can be explained by impurity controlled grain growth. Another main aim of this thesis is to see if the ice
core grain-size with age relations can be used to constrain grain size evolution models, with the ultimate goal
to contribute to the grain size sensitive ice rheology models for large-scale sealevel-forecasting ice sheet models.
The available data of the ice core are compiled and compared with each other. Moreover, a grain size evolution
model is made to include advection processes to grain growth laws. Several correlations and trends are found
between grain size and age, grain size and particle content and grain size and stress. The grain size evolution
model turns out to provide a good estimate for grain size in the Holocene ice of the core, using the best fitting
grain growth law parameters of Diebold (nd). Moreover, the logarithmic trend between grain size and dust
content is a useful tool to estimate the grain size in glacial ice by impurity controlled growth. The grain size in
the Eemian ice is harder to constrain as it seems to be more dynamically controlled, but the paleopiezometer
of Jacka and Jun (1994) can provide a rough estimate. | |
