Dynamics of Deep Recirculation Cells Offshore of the Deep Western Boundary Current in the Subtropical North Atlantic (15°–30°N)
Dynamics of Deep Recirculation Cells Offshore of the Deep Western Boundary Current in the Subtropical North Atlantic (15°–30°N)
复制标题
北大西洋副热带(15°～30°N)西深边界流近海深再循环单元动力学
DOI：
10.1175/jpo-d-20-0184.1
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发表时间：
2021
影响因子：
3.5
通讯作者：
Zhao, Jian
中科院分区：
文献类型：
--
作者：
Biló, Tiago Carrilho;Johns, William E;Zhao, Jian
通过两种不同的涡旋分辨数值模拟研究了北大西洋上部深水层（1000≤z≤3000m）内15°至30°N之间的深西边界流（DWBC）的近海深再循环动力学。尽管再循环单元存在一些差异，但我们对模拟的深层等密度环流模式（36.77≤σ2≤37.06 kg m−3）的评估表明，两种模拟都预测DWBC沿大陆坡向南流动，而所谓的阿巴科环流和另外两个气旋单元则使内陆水域向北再循环。这些单元有几度宽，位于 DWBC 路径上，其特征是沿其平均流线发生位涡 (PV) 变化。对平均 PV 预算的分析表明，这些变化是由涡流强迫作用引起的，该作用往往会侵蚀 PV 水平梯度。研究区域内缺乏主要的上层海洋边界流，而且最强的涡强迫被限制在西部边界数百公里范围内，这表明 DWBC 是涡强迫的主要来源。最后，负责强制再循环的涡流的主导时间尺度在 100 到 300 天之间，这对应于 26.5°N 处 DWBC 传输的主要观测到的变异尺度。
The dynamics of the deep recirculation offshore of the deep western boundary current (DWBC) between 15° and 30°N within the upper North Atlantic Deep Water layer (1000 ≤z≤ 3000 m) is investigated with two different eddy-resolving numerical simulations. Despite some differences in the recirculation cells, our assessment of the modeled deep isopycnal circulation patterns (36.77 ≤σ2≤ 37.06 kg m−3) shows that both simulations predict the DWBC flowing southward along the continental slope, while the so-called Abaco Gyre and two additional cyclonic cells recirculate waters northward in the interior. These cells are a few degrees wide, located along the DWBC path, and characterized by potential vorticity (PV) changes occurring along their mean streamlines. The analysis of the mean PV budget reveals that these changes result from the action of eddy forcing that tends to erode the PV horizontal gradients. The lack of a major upper-ocean boundary current within the study region, and the fact that the strongest eddy forcing is constrained within a few hundreds of kilometers of the western boundary, suggest that the DWBC is the primary source of eddy forcing. Finally, the eddies responsible for forcing the recirculation have dominant time scales between 100 and 300 days, which correspond to the primary observed variability scales of the DWBC transport at 26.5°N.