Marine ice sheet dynamics: Hysteresis and neutral equilibrium
Marine ice sheet dynamics: Hysteresis and neutral equilibrium
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DOI：
10.1029/2008jf001170
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发表时间：
2009-09
影响因子：
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通讯作者：
G. Durand;O. Gagliardini;B. D. Fleurian;T. Zwinger;E. L. Meur
中科院分区：
文献类型：
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作者：
G. Durand;O. Gagliardini;B. D. Fleurian;T. Zwinger;E. L. Meur
[1]海洋冰盖和出口冰川的稳定性主要受其接地线的动力学控制，即，冰的底部接触面从基岩或冰碛变为海水。政府间气候变化专门委员会的上一份报告明确强调，模型捕捉冰川出口动态的能力很差。在这里，我们提出的接地线动力学计算的基础上的数值解的全斯托克斯方程的冰速度，再加上演变的空气冰和海冰的接口。接地线的位置是通过使用有限元程序Elmer求解冰和刚性基岩之间的接触问题来确定的。模拟结果表明，海洋冰盖是不稳定的上斜坡床和冰的粘性扰动下经历滞后，证实了边界层理论的结论。本方法还表明，一个2-D的无侧限海洋冰盖下滑基岩不表现出中性平衡。结果表明，接地线周围的网格分辨率是一个至关重要的问题。为了获得一致的结果，需要非常精细的网格尺寸（<100 m间距）。
[1] The stability of marine ice sheets and outlet glaciers is mostly controlled by the dynamics of their grounding line, i.e., where the bottom contact of the ice changes from bedrock or till to ocean water. The last report of the Intergovernmental Panel on Climate Change has clearly underlined the poor ability of models to capture the dynamics of outlet glaciers. Here we present computations of grounding line dynamics on the basis of numerical solutions of the full Stokes equations for ice velocity, coupled with the evolution of the air ice– and sea ice–free interfaces. The grounding line position is determined by solving the contact problem between the ice and a rigid bedrock using the finite element code Elmer. Results of the simulations show that marine ice sheets are unstable on upsloping beds and undergo hysteresis under perturbation of ice viscosity, confirming conclusions from boundary layer theory. The present approach also indicates that a 2-D unconfined marine ice sheet sliding over a downsloping bedrock does not exhibit neutral equilibrium. It is shown that mesh resolution around the grounding line is a crucial issue. A very fine grid size (<100 m spacing) is needed in order to achieve consistent results.