Numerical Simulation Of Antarctic Ice Sheet Based On The ELMER/ICE Model

The Antarctic ice sheet system plays an important role in the earth system, and investigating its variability and stability has a significant influence on global climate and sea level change. However, there are several traditional research means to investigate the Antarctic ice sheet, such as remote sensing and geophysical methods(including sight rod layout, drilling the ice core in the ice sheet and so on).Remote sensing can obtain a wide range of information of the surface of the ice sheet such as ice flow speed, but due to the lack of penetration, it is difficult to get the inner information of the ice sheet; geophysical methods can get the inner information but it is difficult to obtain a wide range of information, but it costs much time and money.Numerical simulation is a method to investigate and understand the ice sheet dynamics which is based on the balance of the momentum, energy and mass via solving the ice sheet evolution equation. We can have a better understanding to the dynamics and thermodynamics of the ice sheets in different climate conditions. Besides these, numerical simulation can make a better reconstruction for the ice sheet responds to the climate change in the past, and make a better inversion for dynamics and the thermodynamics process of the ice sheet via the observed data which is related to the topography of the ice sheet. On the condition of these, we can better predict the elevation of the ice sheet under different climatic conditions. Compared with these traditional research methods to the Antarctic ice sheet, numerical simulation can provide an effective way to study the ice sheet in large scale in the absence of observed data, this makes numerical simulation become an effective way to research and predict the evolution of the ice sheet.Elmer/ice is a three-dimensional finite element ice model which is based on the Elmer model(a fluid mechanics model) using the triangular mesh to divide the research site. Comparing with the research method which use regularized finite difference solution, the finite element method which use the triangular mesh solution can make a better division to the ice sheet. This paper elaborated the theoretical basis and application of Elmer/ice in detail, and then make several comparative experiments using the two-dimensional Elmer/ice, after this we make an analysis to the modelled results of the two-dimensional experiments and a detail elaboration to the boundary conditions and input parameters. In the end,The main contents of this paper are as follows:1. Firstly, the paper introduces the background and significance of the Antarctic ice sheet research. Secondly, the paper analyses the deficiency of traditional methods in the Antarctic ice sheet. Then, the paper summarizes the current states of Elmer/Ice numerical simulation technology in the Antarctic ice sheet research.2. The paper introduces the key kinematics equation of full-stokes from the point view of the kinematics characteristics of ice sheet. Then, the paper introduces the Glen’s ice flow law, discusses the anisotropy of ice which have an impact on the result of the numerical model simulation. The anisotropic characteristics of the ice polar ice has a great influence on all of ice flow, so the results also can be used to modify the relationship of the age-depth of the ice sheet. Finally the paper brings in the pressure melting point of ice and heat conduction equation in the internal ice. Based on this, we can couple the temperature field for solving the internal temperature field of the ice sheet.3. The Elmer/Ice model conducts a simple two-dimensional ice sheet velocity field without considering the boundary conditions and the constraint conditions of ice sheet; then with considering the slip conditions at the bottom of the ice sheet to simulate the flow field of ice again; in the following simulation we set a pressure melt point for the ice sheet in the assumption that the ice sheet is consist of entire ice. Finally we compare considering the process with heat transfer which introduces the temperature parameter with only considering the process of heat transfer, then evaluate the simulation results in the different conditions(boundary condition, constraint condition, physical process and so on).4. The paper makes a simulation to the three-dimensional Tete Rousse ice sheet using Elmer/Ice model, the simulation condition is closer to the true ice sheet. Comparing the simulation results of the ice velocity field and the pressure field with the true data, we obtain an assessment of the input parameters, the boundary conditions and the terrain conditions of the simulating ice model in the process of simulating the actual ice sheet.5. We use a three-dimensional finite element model which has successfully obtained the inner velocity and inner temperature field of the Antarctic ice sheet to investigate the section which begins from Dome A and ends in Zhong Shan station(including a lot of important and valuable research sites, for example, the upstream of the Lambert glacier, the Gamburtsev Mountains, Dome A). We can find that the modelled data is identical to the observed data. The bottom temperature of the most part in this area has reached the pressure melting point. The velocity of the inland ice sheet is small. Near the ice shelf, the horizontal velocity has a sudden increase while the vertical velocity changes only in the case of the bottom morphology having a sudden change. This conclusion meets the tendency of the Antarctic ice sheet movement, on the condition of this, Elmer/ice is suitable for modelling the Antarctic ice sheet.