科研之友
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摘要
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.
- 出版日期2018-6
- 单位国家气候中心
