Dense water downslope flow and AABW production in a numerical model: Sensitivity to horizontal and vertical resolution in the region off Cape Darnley polynya
Dense water downslope flow and AABW production in a numerical model: Sensitivity to horizontal and vertical resolution in the region off Cape Darnley polynya
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数值模型中的浓水下坡流和 AABW 产生：达恩利角冰间湖区域对水平和垂直分辨率的敏感性
DOI：
10.1016/j.ocemod.2021.101843
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发表时间：
2021
期刊：
影响因子：
3.2
通讯作者：
Ohshima Kay I.
中科院分区：
文献类型：
--
作者：
Mensah Vigan;Nakayama Yoshihiro;Fujii Masakazu;Nogi Yoshifumi;Ohshima Kay I.
南大洋密集陆架水（DSW）和南极底层水（AABW）的形成是温盐环流的重要组成部分，了解这一现象对研究全球气候至关重要。AABW是由于DSW沿大陆坡流下并与周围沃茨混合而形成的。然而，DSW的形成和它的下降仍然是许多海洋模式中解决不好的问题。因此，我们模拟了DSW的形成和下降，并研究了模式对水平和垂直网格间距的敏感性。马萨诸塞州理工学院的大气环流模型（MITgcm）用于东南极洲达恩利角外的区域，该区域是AABW的主要生产区之一，历史和系泊数据可用于比较。粗水平网格分辨率的顺序（10公里）的模拟产生了大量的DSW的货架上。然而，这个DSW的大部分被转化为中层水和平流向西。水平模式分辨率等于或高于2公里，需要模拟DSW的下降和现实的AABW生产。位于2，600米深处的系泊处的模拟时间序列显示，速度和温度的周期性波动分别为0.3 m·s-1和0.5° C，与观测结果一致。我们还发现，高分辨率的测深数据集是至关重要的，因为新形成的AABW体积减少了20%时，更平滑的测深使用2公里分辨率的网格。垂直分辨率对模式性能的影响很小，因为烟羽比网格宽度厚得多（> 170米）。因此，在水平分辨率较高（≤ 2 km）和垂直分辨率较粗（大陆坡上为100 m）的情况下，可以再现Cape Darnley地区DSW和AABW地层的下坡流。
Abstract The formation of Dense Shelf Water (DSW) and Antarctic Bottom Water (AABW) in the Southern Ocean is an essential part of the thermohaline circulation, and understanding this phenomenon is crucial for studying the global climate. AABW is formed as DSW flows down the continental slope and mixes with the surrounding waters. However, DSW formation and its descent remains a poorly resolved issue in many ocean models. We, therefore, simulated the formation and descent of DSW and investigated the model sensitivities to horizontal and vertical grid spacings. The Massachusetts Institute of Technology general circulation model (MITgcm) was used for the region off Cape Darnley in East Antarctica, one of the main AABW production areas, where historical and mooring data are available for comparison. Simulations with coarse horizontal grid resolutions of order (10 km) yielded high volumes of DSW on the shelf. However, the largest part of this DSW was transformed into intermediate water and advected westward. Horizontal model resolutions equal to or higher than 2 km were required to simulate the descent of DSW and a realistic AABW production. Simulated time series at a mooring located at a depth of 2,600 m showed periodic fluctuations in velocity and temperature of 0.3 m⋅ s− 1 and 0.5° C, respectively, consistent with observations. We also found that high-resolution bathymetry datasets are crucial because the newly formed AABW volume was reduced by 20% when a smoother bathymetry was used on a 2-km resolution grid. Vertical resolution had little influence on model performance because the plume was much thicker (> 170 m) than the grids width. Therefore, reproducing the downslope flow of DSW and AABW formation in the Cape Darnley region can be achieved with a high horizontal resolution (≤ 2 km) and a relatively coarse vertical resolution (∼ 100 m on the continental slope).
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