Does Topographic Form Stress Impede Prograde Ocean Currents?
Does Topographic Form Stress Impede Prograde Ocean Currents?
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DOI：
10.1175/jpo-d-20-0189.1
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发表时间：
2021-08-01
影响因子：
3.5
通讯作者：
Stewart, Andrew L.
中科院分区：
文献类型：
--
作者：
Bai, Yue;Wang, Yan;Stewart, Andrew L.
地形应力（TFS）在限制南极绕极流（ACC）的输送以及主要洋盆之间的交换率方面发挥着核心作用。 ACC 中地形应力的产生与罗斯贝驻波的形成有关，罗斯贝驻波的发生是因为水流是逆行的（与罗斯贝波传播的方向相反）。然而，目前尚不清楚 TFS 是否会同样阻碍当前的顺行系统（沿罗斯贝波传播方向），而该系统无法阻止罗斯贝波。等重模型用于研究纬向通道中风驱动的顺行和逆行流的动量平衡，测深由单个山脊或具有经向偏移的大陆架和斜坡组成。与之前的研究一致，除了平坦测深的限制外，逆行流几乎完全受到 TFS 的阻碍，而顺行流通常受到 TFS 和底部摩擦力的共同阻碍。驻波的正压理论表明，底部摩擦力可以使驻波压力场的相位从测深压力场的相位发生变化，这是产生 TFS 所必需的。该机制在顺流和逆流中是相同的，但当平均流阻止波长与测深波长相当的罗斯贝波时，效率最高。顺行和逆行动量平衡之间的不对称意味着顺行流系统可能对风力强迫的变化更加敏感，例如与气候变化相关的风力强迫变化。
Topographic form stress (TFS) plays a central role in constraining the transport of the Antarctic Circumpolar Current (ACC), and thus the rate of exchange between the major ocean basins. Topographic form stress generation in the ACC has been linked to the formation of standing Rossby waves, which occur because the current is retrograde (opposing the direction of Rossby wave propagation). However, it is unclear whether TFS similarly retards current systems that are prograde (in the direction of Rossby wave propagation), which cannot arrest Rossby waves. An isopycnal model is used to investigate the momentum balance of wind-driven prograde and retrograde flows in a zonal channel, with bathymetry consisting of either a single ridge or a continental shelf and slope with a meridional excursion. Consistent with previous studies, retrograde flows are almost entirely impeded by TFS, except in the limit of flat bathymetry, whereas prograde flows are typically impeded by a combination of TFS and bottom friction. A barotropic theory for standing waves shows that bottom friction serves to shift the phase of the standing wave's pressure field from that of the bathymetry, which is necessary to produce TFS. The mechanism is the same in prograde and retrograde flows, but is most efficient when the mean flow arrests a Rossby wave with a wavelength comparable to that of the bathymetry. The asymmetry between prograde and retrograde momentum balances implies that prograde current systems may be more sensitive to changes in wind forcing, for example associated with climate shifts.