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首页> 外文期刊>Journal of Physical Oceanography >Observations of Ekman Currents in the Southern Ocean
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Observations of Ekman Currents in the Southern Ocean

机译：南洋埃克曼流的观测

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Largely zonal winds in the Southern Ocean drive an equatorward Ekman transport that constitutes the shallowest limb of the meridional overturning circulation of the Antarctic Circumpolar Current (ACC). Despite its importance, there have been no direct observations of the open ocean Ekman balance in the Southern Ocean until now. Using high-resolution repeat observations of upper-ocean velocity in Drake Passage, a mean Ekman spiral is resolved and Ekman transport is computed. The mean Ekman currents decay in amplitude and rotate anticyclonically with depth, penetrating to ～100-m depth, above the base of the annual mean mixed layer at 120 m. The rotation depth scale exceeds the e-folding scale of the speed by about a factor of 3, resulting in a current spiral that is compressed relative to predictions from Ekman theory. Transport estimated from the observed currents is mostly equatorward and in good agreement with the Ekman transport computed from four different gridded wind products. The mean temperature of the Ekman layer is not distinguishable from temperature at the surface. Turbulent eddy viscosities inferred from Ekman theory and a direct estimate of the time-averaged stress were O(10~2-10~3) cm~2 s~(-1). The latter calculation results in a profile of eddy viscosity that decreases in magnitude with depth and a time-averaged stress that is not parallel to the time-averaged vertical shear. The compression of the Ekman spiral and the nonparallel shear-stress relation are likely due to time averaging over the cycling of the stratification in response to diurnal buoyancy fluxes, although the action of surface waves and the oceanic response to high-frequency wind variability may also contribute.
机译：南大洋的大部分纬向风驱动着赤道埃克曼输运，它构成了南极绕极洋流（ACC）的子午翻转环流的最浅肢。尽管它很重要，但是到目前为止，还没有直接观测到南大洋中埃克曼海域的平衡。使用对德雷克海峡中上层海洋速度的高分辨率重复观测，可以解析平均埃克曼螺旋并计算埃克曼输运。平均Ekman电流的振幅会衰减并随深度反循环旋转，并穿透到年均混合层底部120 m处约100 m的深度。旋转深度标度超过速度的电子折叠标度约3倍，导致当前螺旋相对于Ekman理论的预测被压缩。根据观测到的潮流估计的运输量大多是赤道的，并且与根据四种不同的网格风产品计算出的埃克曼运输量非常一致。埃克曼层的平均温度与表面温度没有区别。由Ekman理论推导的湍流涡流粘度和时间平均应力的直接估计值是O（10〜2-10〜3）cm〜2 s〜（-1）。后者的计算得出的涡流粘度曲线随着深度的增加而减小，并且时间平均应力与时间平均垂直剪切力不平行。 Ekman螺旋的压缩和非平行剪切应力关系很可能是由于分层对昼夜浮力通量的响应时间平均而引起的，尽管表面波的作用和海洋对高频风变率的响应也可能是由于有助于。

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