Modeling the transport of passive tracers in sea ice
Modeling the transport of passive tracers in sea ice
复制标题
模拟海冰中被动示踪剂的传输
DOI：
10.1029/2010jc006527
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发表时间：
2011
影响因子：
--
通讯作者：
S. Elliott
中科院分区：
文献类型：
--
作者：
N. Jeffery;E. Hunke;S. Elliott
[1]本文提出了一个海冰中被动示踪剂垂直输运的模式。针对新的冰示踪剂模式（IceT）中的示踪剂速度弥散项，提出了两种雷诺通量封闭近似。“增强分子扩散”（EMD）和“混合长度扩散”（MLD）方案是重力排水的参数化方案，重力排水是海冰生长过程中脱盐的主要机制。IceT使用每个参数化的性能测试对两个实验研究：模拟我比较配置文件的盐水盐度与被动示踪剂浓度在海冰的生长和融化，和模拟II比较底部边界盐和盐水体积通量与被动示踪剂通量和底部扩散。IceT的行为进行了评估下三个盐度强迫处方。这两个方案成功地再现预期的示踪剂浓度在模拟I时，盐度强迫的演变。然而，在模拟II中，MLD方案在两个重要方面优于EMD：1）MLD扩散率平行测量盐水体积通量的增长率趋势，而EMD底部扩散率几乎保持不变;和2）MLD底部示踪剂浓度随着冰的增长率下降，类似于排除盐水盐度，而EMD趋势相反。因此，增强的分子扩散是非常值得怀疑的反应性被动示踪剂模型中的实施。IceT混合长度扩散系数是海冰地球化学模拟中一个可行的选择。它仍然是一个挑战，以评估是否MLD可以提供定量估计脱盐在每个时间步骤中使用强制IceT或在海冰盐度模型的实施。
[1] A model for the vertical transport of passive tracers in sea ice is presented. Two Reynolds flux closure approximations are proposed for the tracer velocity dispersion term in the new ice tracer model (IceT). The schemes, “enhanced molecular diffusion” (EMD) and “mixing length diffusion” (MLD), are suggested parameterizations of gravity drainage, the dominant mechanism of desalination in growing sea ice. The performance of IceT using each parameterization is tested against two experimental studies: simulations I compare profiles of brine salinity with passive tracer concentrations during sea ice growth and melt, and simulations II compare bottom boundary salt and brine volume fluxes with passive tracer fluxes and bottom diffusivities. IceT behavior is evaluated under three salinity forcing prescriptions. Both schemes successfully reproduce expected tracer concentrations in simulations I when the salinity forcing evolves logarithmically. However in simulations II, the MLD scheme outperforms EMD in two significant ways: 1) growth rate trends in the MLD diffusivity parallel measurements of brine volume flux, while EMD bottom diffusivities remain almost constant; and 2) MLD bottom tracer concentrations decrease with ice growth rate similar to excluded brine salinity, while EMD trends are contrary. Hence, enhanced molecular diffusion is highly questionable for implementation in models of reactive passive tracers. The IceT mixing length diffusivity is a viable choice in sea ice biogeochemical modeling. It remains a challenge to assess whether MLD can provide quantitative estimates of desalination at each time step for use in forcing IceT or for implementation in a model of sea ice salinity.