The Role of Closed Gyres in Setting the Zonal Transport of the Antarctic Circumpolar Current
The Role of Closed Gyres in Setting the Zonal Transport of the Antarctic Circumpolar Current
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DOI：
10.1175/jpo-d-14-0173.1
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发表时间：
2015-06-01
影响因子：
3.5
通讯作者：
Ferrari, Raffaele
中科院分区：
文献类型：
--
作者：
Nadeau, Louis-Philippe;Ferrari, Raffaele
涡允许的模拟表明，盆状涡旋可以观察到的大尺度正压气流的风驱动的渠道与地形脊。这证实了两层准地转和25层原始方程模式在高水平分辨率。比较有无地形脊的模拟结果表明，当海底地形平坦时，海峡中的纬向斜压输送随风应力的增加而增加，而当有地形脊时，则不随风应力的增加而增加。随着大尺度正压流函数中再循环环流的发展，增加风的输送饱和发生。这表明总环流可以被认为是环流模式（环极输送为零）和自由环极模式（包含所有输送）的叠加。由于地形引导正压流线，并支持类似于沿着西部边界观察到的更熟悉的摩擦边界层，因此在海峡中出现盆状环流。因此，环流模式与沿脊流所施加的底形应力密切相关，并为风动量输入提供汇。在这个框架内，风力的任何增加都会产生更强的环流，而不是为绕极输送提供食物。这一假设得到了一系列实验的支持，其中的关键参数进行了广泛的范围内：风应力，风应力旋度，山脊高度，通道长度和底部摩擦。
Eddy-permitting simulations are used to show that basinlike gyres can be observed in the large-scale barotropic flow of a wind-driven channel with a meridional topographic ridge. This is confirmed using both two-layer quasigeostrophic and 25-level primitive equation models at high horizontal resolution. Comparing results from simulations with and without the topographic ridge, it is shown that the zonal baroclinic transport in the channel increases with increasing wind stress when the bottom topography is flat but not when there is a meridional ridge. The saturation of transport for increasing wind occurs in conjunction with the development of recirculating gyres in the large-scale barotropic streamfunction. This suggests that the total circulation can be thought of as a superposition of a gyre mode (which has zero circumpolar transport) and a free circumpolar mode (which contains all of the transport). Basinlike gyres arise in the channel because the topography steers the barotropic streamlines and supports a frictional boundary layer similar to the more familiar ones observed along western boundaries. The gyre mode is thus closely linked with the bottom form stress exerted by the along-ridge flow and provides the sink for the wind momentum input. In this framework, any increase in wind forcing spins a stronger gyre as opposed to feeding the circumpolar transport. This hypothesis is supported with a suite of experiments where key parameters are carried over a wide range: wind stress, wind stress curl, ridge height, channel length, and bottom friction.