Turbulence in the Ice Shelf-Ocean Boundary Current and Its Sensitivity to Model Resolution
Turbulence in the Ice Shelf-Ocean Boundary Current and Its Sensitivity to Model Resolution
复制标题
冰架-海洋边界流中的湍流及其对模型分辨率的敏感性
DOI：
10.1175/jpo-d-22-0034.1
复制
发表时间：
2023
影响因子：
3.5
通讯作者：
Patmore R
中科院分区：
文献类型：
--
作者：
Patmore R
冰架-海洋边界流对冰架底部的热量输送具有重要的控制作用。包括冰架空腔表示的气候和区域模型通常使用粗网格，其结果强烈依赖于冰架-海洋界面附近的分辨率。本研究以允许湍流的分辨率（1 m）以非静水力水平配置模拟冰架-海洋边界流。与最先进的大涡流模拟相比，Z 级模型表现良好，显示出其代表正确物理场的能力。我们表明，具有参数化湍流的一维模型的理论结果在很大程度上再现了 z 级模型结果，表明作为湍流闭合的可能实用性。一维模型演变成边缘不稳定状态，我们使用 z 级模型来演示如何在三个维度中表示这一状态。不稳定性的出现调节了重斜层的强度，并与持续的埃克曼滚转共存，这些不稳定性在流动变得间歇性不稳定之前就被识别出来。当降低 z 级模型的分辨率以了解网格尺度依赖性时，退化主要是由过度数值扩散的既定问题决定的。我们表明，在中等分辨率（2-4 m）下，可以通过调整扩散率来部分恢复边界层结构。最后，我们比较了用取决于当地海洋条件的交互式融化来代替规定的融化。交互式熔化会产生反馈，使系统演化更慢，这种反馈在较低分辨率下会被夸大。
The ice shelf–ocean boundary current has an important control on heat delivery to the base of an ice shelf. Climate and regional models that include a representation of ice shelf cavities often use a coarse grid, and results have a strong dependence on resolution near the ice shelf–ocean interface. This study models the ice shelf–ocean boundary current with a nonhydrostaticz-level configuration at turbulence-permitting resolution (1 m). Thez-level model performs well when compared against state-of-the-art large-eddy simulations, showing its capability in representing the correct physics. We show that theoretical results from a one-dimensional model with parameterized turbulence reproduce thez-level model results to a good degree, indicating possible utility as a turbulence closure. The one-dimensional model evolves to a state of marginal instability, and we use thez-level model to demonstrate how this is represented in three dimensions. Instabilities emerge that regulate the strength of the pycnocline and coexist with persistent Ekman rolls, which are identified prior to the flow becoming intermittently unstable. When resolution of thez-level model is degraded to understand the gridscale dependencies, the degradation is dominated by the established problem of excessive numerical diffusion. We show that at intermediate resolutions (2–4 m), the boundary layer structure can be partially recovered by tuning diffusivities. Last, we compare replacing prescribed melting with interactive melting that is dependent on the local ocean conditions. Interactive melting results in a feedback such that the system evolves more slowly, which is exaggerated at lower resolution.