Wave rafting and the equilibrium pancake ice cover thickness
Wave rafting and the equilibrium pancake ice cover thickness
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DOI：
10.1029/2003jc002192
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发表时间：
2004-07-31
影响因子：
3.6
通讯作者：
Ackley, SF
中科院分区：
文献类型：
--
作者：
Dai, MR;Shen, HH;Ackley, SF
薄饼冰是冰在波场中生长过程中形成的圆形浮冰，在许多极地和副极地海洋中形成。从这些区域的冰盖中获取的岩心的垂直薄片显示出明显的分层结构。这些观察结果表明，波浪漂流在确定冰盖厚度方面可以发挥重要作用，其作用比热力学生长更重要。尽管波浪漂流直观上是显而易见的，但之前尚未进行将由此产生的冰盖与波浪特征联系起来的研究。在这项研究中，我们利用实验室实验和数值模拟来确定漂流过程。我们提出了一种预测最终平衡厚度的理论，前提是入射波保持恒定。理论上的平衡厚度与波幅的平方和絮体直径的平方成正比，与波长的立方成反比。该理论将最终的冰盖厚度与波浪特征以及薄状浮冰的尺寸和表面特性联系起来。该理论还提供了一种计算单层薄状浮冰和平衡筏式冰盖之间的边界传播速度的方法。我们用塑料模型薄饼冰进行实验室实验来制作漂流。我们使用三维离散元模型进行计算机模拟，模拟波场中圆盘状浮冰的运动。我们将理论结果与实验室实验和数值模拟漂流过程进行比较。实验室和计算机模拟结果均与理论相比较。
Pancake ice, the circular floes formed during ice growth in a wave field, forms in many polar and subpolar seas. Vertical thin sections of cores taken from the ice cover in these regions show distinct layering structure. These observations suggest wave rafting could play a significant role in defining the ice cover thickness, much more so than thermodynamic growth. Although wave rafting is intuitively apparent, no previous study relating the resulting ice cover to wave characteristics has been conducted. In this study we utilize both laboratory experiments and numerical simulations to determine the rafting process. We propose a theory that predicts a final equilibrium thickness, provided that the incoming wave is kept constant. The equilibrium thickness from the theory is proportional to the square of the wave amplitude and the square of the floe diameter and is inversely proportional to the cube of the wavelength. This theory relates the final ice cover thickness to the wave characteristics and the size and surface properties of the pancake ice floes. This theory also provides a way to calculate the speed with which the boundary between the single-layer pancake ice floes and the equilibrium rafted ice cover propagates. We conduct laboratory experiments with plastic model pancake ice to create rafting. We perform computer simulations with a three-dimensional discrete element model that simulates the movement of disc-shaped floes in the wave field. We compare the theoretical result with the laboratory experiments and a numerically simulated rafting process. Both the laboratory and the computer simulation results compare favorably with the theory.