Deep‐water dynamics and boundary mixing in a nontidal stratified basin: A modeling study of the Baltic Sea
Deep‐water dynamics and boundary mixing in a nontidal stratified basin: A modeling study of the Baltic Sea
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非潮汐分层盆地的深水动力学和边界混合：波罗的海的模拟研究
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
L. Umlauf
中科院分区：
文献类型：
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作者：
P. Holtermann;H. Burchard;U. Gräwe;K. Klingbeil;L. Umlauf
最近一项示踪剂释放实验的结果表明，与许多湖泊和海洋盆地类似，波罗的海的深水混合在很大程度上是由发生在能量充沛的近海底区域的混合过程决定的。然而，由于该区域的复杂性和较小的垂直范围，以前对波罗的海的模拟研究迄今未能在数值和物理上提供边界混合的可靠表示。在这里，我们讨论了波罗的海中部嵌套高分辨率模拟的第一个结果，该模拟旨在借助新的数值技术（自适应坐标）和最先进的湍流模型对湍流底边界层进行真实描述。利用波罗的海示踪剂释放实验的综合数据集，我们表明该模型能够以极好的精度再现关键的动力学过程（近惯性波、地形波和边缘流）。研究发现，由这些过程引发的边界混合导致模拟的盆地尺度混合率与观测结果非常吻合，其中包括以往研究中强调的季节变率。这些结果也可能与描述大型湖泊和其他分层盆地的混合有关。
Recent results from a tracer release experiment have shown that, similar to many lakes and ocean basins, deep-water mixing in the Baltic Sea is largely determined by mixing processes occurring in the energetic near-bottom region. Due to the complexity and small vertical extent of this region, however, previous modeling studies of the Baltic Sea have so far not been able to provide a numerically and physically sound representation of boundary mixing. Here we discuss first results from a nested high-resolution simulation of the central Baltic Sea that aims at a realistic description of the turbulent bottom boundary layer with the help of new numerical techniques (adaptive coordinates) and state-of-the-art turbulence modeling. Using a comprehensive data set from the Baltic Sea Tracer Release Experiment, we show that the model is able to reproduce the key dynamical processes (near-inertial waves, topographic waves, and a rim current) with excellent accuracy. Boundary mixing triggered by these processes was found to result in simulated basin-scale mixing rates in close agreement with observations, including a seasonal variability that has been emphasized in previous studies. These results may be relevant also for the description of mixing in large lakes and other stratified basins.