An Emergent Sea Ice Floe Size Distribution in a Global Coupled Ocean-Sea Ice Model
An Emergent Sea Ice Floe Size Distribution in a Global Coupled Ocean-Sea Ice Model
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DOI：
10.1029/2017jc013692
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发表时间：
2018-06-01
影响因子：
3.6
通讯作者：
Bitz, Cecilia M.
中科院分区：
文献类型：
--
作者：
Roach, Lettie A.;Horvat, Christopher;Bitz, Cecilia M.
海冰由离散的浮冰组成，其大小跨越数量级。在这里，我们提出了一个模型，代表海冰厚度和浮冰大小的联合分布。与以往的研究不同，我们不强加一个特定的形式上的亚网格尺度浮冰大小分布。浮冰的大小是由五个关键物理过程的相互作用决定的：新冰的形成，浮冰在冻结条件下的焊接，横向生长和融化，以及海洋表面波引起的浮冰断裂。耦合模型的结果表明，这些过程捕获的浮冰大小分布的一阶特征，包括衰减的分布，增加浮冰大小和全流域的空间变异的代表性半径。横向熔化和絮凝物焊接是特别重要的，其中波浪断裂以优选的尺寸产生絮凝物。除了浮冰大小的依赖，现有的模型物理结果显着减少海冰浓度，特别是在夏季，主要是由于浮冰大小依赖的横向融化。横向融化的增加改变了融化潜力的分配，从而减少了基底融化，并增加了某些地区的海冰厚度。这些结果表明，包括浮冰的大小分布可能是重要的极地气候系统的准确模拟。简明语言摘要气候模式模拟海洋，大气，陆地表面和海冰之间的复杂相互作用在垂直和水平网格。在一个典型的水平分辨率大约为1经纬度的模型网格单元中，海冰组件目前只模拟了任何冰的不同厚度。现实生活中的海冰覆盖是由称为浮冰的离散冰块组成的，这些冰块的水平尺寸变化很大。在这里，我们提出了一个新的海冰模型，模拟浮冰的大小以及厚度。当新冰形成、冰融化或冻结，或者当浮冰被海浪打破时，浮冰的大小会发生变化。新模型改变了对大规模海冰特性的模拟，这对于准确表示极地气候非常重要。
Sea ice is composed of discrete floes, which range in size across orders of magnitude. Here we present a model that represents the joint distribution of sea ice thickness and floe size. Unlike previous studies, we do not impose a particular form on the subgrid-scale floe size distribution. Floe sizes are determined prognostically by the interaction of five key physical processes: new ice formation, welding of floes in freezing conditions, lateral growth and melt, and fracture of floes by ocean surface waves. Coupled model results suggest that these processes capture first-order characteristics of the floe size distribution, including decay in the distribution with increasing floe size and basin-wide spatial variability in representative radius. Lateral melt and floe welding are particularly important, with wave fracture creating floes at preferred sizes. The addition of floe size dependence to the existing model physics results in significant reductions in sea ice concentration, particularly in summer and principally due to floe size-dependent lateral melt. The increased lateral melt alters partitioning of the melting potential, which reduces basal melt and increases sea ice thickness in some locations. These results suggest that including a floe size distribution may be important for accurate simulation of the polar climate system.Plain Language Summary Climate models simulate complex interactions between the ocean, atmosphere, land surface, and sea ice on vertical and horizontal grids. Within a model grid cell, which is typically around 1 degrees latitude/longitude horizontal resolution, the sea ice component currently only simulates the different thicknesses of any ice present. Real-life sea ice cover is made up of discrete pieces of ice called floes, which can have widely varying horizontal sizes. Here we present a new sea ice model which simulates both floe sizes as well as thicknesses. Floe sizes change when new ice is created, ice melts or freezes, or when floes are broken up by ocean waves. The new model alters the simulation of large-scale sea ice properties, which could be important for accurate representation of polar climate.