open access

https://doi.org/10.14943/doctoral.k8702

https://hdl.handle.net/2115/34136

氷床流動による氷の異方性と構造変化を考慮したフルストークス有限要素法モデルの構築と，南極氷床・ドームふじ近傍への適用

英語

2008-03-25

Hokkaido University

This thesis is revised in August 2009. Please follow the link below.

A three-dimensional, thermo-mechanically coupled flow model with induced anisotropy has been developed and applied to the vicinity of Dome Fuji, Antarctica, the site of a recent Japanese deep ice drilling project. The model implements the full-Stokes equations for the ice dynamics, and the system is solved with the finite-element method (FEM) using the open source multi-physics package Elmer. A Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor (CAFFE model) is used for taking into account flow-induced anisotropy in ice. The flow law is implemented in Elmer/Ice by means of second and fourth order orientation tensors that describe the c-axis orientation of the fabric. Similarly, the fabric evolution equation is written in terms of the evolution of the second order tensor, and it is solved inside Elmer/Ice with a Discontinuous Galerkin method using Picard type iterations for the non-linearity. Since the fabric evolution equation also depends on the fourth order orientation tensor, the IBOF (Invariant-Based Optimal Fitting) closure function is used for the computation of its components from the solution of the second orientation. The main questions addressed by the simulations carried out in this thesis are (i) what is the local flow field in the vicinity of Dome Fuji, (ii) how is the flow field affected by the anisotropic fabric, and (iii) what are the consequences for the interpretation of the climatological proxy data of the Dome Fuji ice core. The results are therefore relevant for the reconstruction of the paleo-climatic variability in East Antarctica, which is an important clue for understanding possible future climate changes on Earth. Further, the improved modeling of ice dynamics by solving the full-Stokes equations and including anisotropy is an important step towards simulating rapid dynamical changes which may destabilize the terrestrial ice sheets and lead to a potentially dangerous rate of sea level rise in a warming environment.

2008-03-25

甲第8702号

博士(環境科学)

博士論文

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