Impact of Horizontal Model Resolution on Mixing and Dispersion in the Northeastern Gulf of Mexico

IF 3.3 2区 地球科学 Q1 OCEANOGRAPHY
Nektaria Ntaganou, Eric P. Chassignet, Alexandra Bozec
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Abstract

In this paper, the importance of model horizontal resolution in mixing and dispersion is investigated by comparing two data-assimilative high-resolution simulations (4 and 1 km), one of which is submesoscale-permitting. By employing both Eulerian and Lagrangian metrics, upper-ocean differences between the mesoscale-resolving and submesoscale-permitting simulations are examined in the northeastern Gulf of Mexico, a region of high mesoscale and submesoscale activity. Mixing in both simulations is explored by conducting Lagrangian experiments to track the generation of Lagrangian coherent structures (LCSs) and their associated transport barriers. Finite-time Lyapunov exponent (FTLE) fields show higher separation rates of fluid particles in the submesoscale-permitting case, which indicate more vigorous mixing with differences being more pronounced in the shelf regions (depths ≤ 500 m). The extent of the mixing homogeneity is examined using probability density functions (PDFs) of FTLEs with results suggesting that mixing is heterogeneous in both simulations, but some homogeneity is exhibited in the submesoscale-permitting case. The FTLE fields also indicate that chaotic advection dominates turbulent mixing in both simulations regardless of the horizontal resolution. In the submesoscale-permitting experiment, however, smaller scale LCSs emerge as noise-like filaments that suggest a larger turbulent mixing component than in the mesoscale-resolving experiment. The impact of resolution is then explored by investigating the spread of oil particles at the location of the Deepwater Horizon oil spill.

Abstract Image

水平模式分辨率对墨西哥湾东北部混合和扩散的影响
本文通过比较两种数据同化高分辨率模拟(4 公里和 1 公里)(其中一种为次中尺度模拟),研究了模式水平分辨率在混合和扩散中的重要性。通过采用欧拉和拉格朗日指标,研究了墨西哥湾东北部中尺度和次中尺度活动频繁地区中尺度解算模拟和次中尺度模拟之间的上层海洋差异。通过进行拉格朗日实验,跟踪拉格朗日相干结构(LCS)及其相关传输障碍的生成,探索了两种模拟中的混合情况。有限时间李亚普诺夫指数(FTLE)场显示,在允许次中尺度的情况下,流体颗粒的分离率更高,这表明混合更剧烈,在陆架区域(深度≤ 500 米)差异更明显。使用 FTLE 的概率密度函数(PDFs)对混合均匀性的程度进行了检验,结果表明,在两种模拟情况下,混合是异质的,但在亚中尺度允许情况下表现出一定的均匀性。FTLE 场还表明,在两种模拟中,无论水平分辨率如何,混沌平流都主导着湍流混合。然而,在亚中尺度允许实验中,较小尺度的 LCS 出现了类似噪声的细丝,表明湍流混合成分大于中尺度分辨率实验中的湍流混合成分。然后,通过研究深水地平线漏油地点的石油颗粒扩散情况,探讨了分辨率的影响。
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来源期刊
Journal of Geophysical Research-Oceans
Journal of Geophysical Research-Oceans Earth and Planetary Sciences-Oceanography
CiteScore
7.00
自引率
13.90%
发文量
429
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