Tidal Mixing in the Kuril Straits and Its Impact on Ventilation in the North Pacific Ocean
Tidal Mixing in the Kuril Straits and Its Impact on Ventilation in the North Pacific Ocean
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DOI：
10.1023/b:joce.0000038225.15056.c6
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发表时间：
2004-04
影响因子：
2.3
通讯作者：
Tomohiro Nakamura;T. Toyoda;Y. Ishikawa;T. Awaji
中科院分区：
文献类型：
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作者：
Tomohiro Nakamura;T. Toyoda;Y. Ishikawa;T. Awaji
本文用三维非静力模式对千岛海峡及其附近K1潮流产生的斜压过程进行了数值研究。结果表明，在整个沿着千岛岛链上产生了大振幅的非定常背风波，并引起强烈的贯向混合，最大贯向扩散系数超过103 cm 2 s −1。在浅水区的剧烈混合的显着的水转化产生了明显的密度和位涡（PV）沿沿着岛链锋。从锋面产生并远离锋面的夹断涡旋有能力将大量混合水（1014 Sv）输送到近海地区，大约一半被引导到北太平洋。这些特征与最近的卫星图像和现场观测结果相一致，表明千岛群岛附近的贯叶混合比以前认为的鄂霍次克海和北太平洋的影响更大。为了研究千岛群岛潮汐过程对邻近两个海盆环流的影响，利用海洋环流模式进行了另一个数值试验，该模式考虑了沿着岛屿的潮汐混合，比不考虑潮汐混合的情况更好地代表了鄂霍次克海模式水。这主要是由于一个显着的向上盐通量到表层由于在千岛海峡，随后被运送到鄂霍次克海的内部区域的潮汐混合的附加效果。冬季鄂霍次克海北方部分的冷却可以产生更重的水，从而增强俯冲作用，这能够再现现实的鄂霍次克海模式水。从千岛海峡到开阔的北太平洋的低PV通量除了激发第一模态外，还激发了第二阶斜压模态Kelvin和Rossby波。有趣的是，在北太平洋的纬向翻转加强作为由这些波引起的动力学调整的结果，导致更真实的再现北太平洋中层水（NPIW）比在没有潮汐混合的情况下。因此，潮汐引起的传输和转换占主导地位的千岛海峡和随后的涡旋输送的联合作用被认为是在鄂霍次克海和北太平洋的通风中发挥重要作用。
A numerical study using a 3-D nonhydrostatic model has been applied to baroclinic processes generated by theK1tidal flow in and around the Kuril Straits. The result shows that large-amplitude unsteady lee waves are generated and cause intense diapycnal mixing all along the Kuril Island Chain to levels of a maximum diapycnal diffusivity exceeding 103cm2s−1. Significant water transformation by the vigorous mixing in shallow regions produces the distinct density and potential vorticity (PV) fronts along the Island Chain. The pinched-off eddies that arise and move away from the fronts have the ability to transport a large amount of mixed water (∼14 Sv) to the offshore regions, roughly half being directed to the North Pacific. These features are consistent with recent satellite imagery and in-situ observations, suggesting that diapycnal mixing within the vicinity of the Kuril Islands has a greater impact than was previously supposed on the Okhotsk Sea and the North Pacific. To examine this influence of tidal processes at the Kurils on circulations in the neighboring two basins, another numerical experiment was conducted using an ocean general circulation model with inclusion of tidal mixing along the islands, which gives a better representation of the Okhotsk Sea Mode Water than in the case without the tidal mixing. This is mainly attributed to the added effect of a significant upward salt flux into the surface layer due to tidal mixing in the Kuril Straits, which is subsequently transported to the interior region of the Okhotsk Sea. With a saline flux into the surface layer, cooling in winter in the northern part of the Okhotsk Sea can produce heavier water and thus enhance subduction, which is capable of reproducing a realistic Okhotsk Sea Mode Water. The associated low PV flux from the Kuril Straits to the open North Pacific excites the 2nd baroclinic-mode Kelvin and Rossby waves in addition to the 1st mode. Interestingly, the meridional overturning in the North Pacific is strengthened as a result of the dynamical adjustment caused by these waves, leading to a more realistic reproduction of the North Pacific Intermediate Water (NPIW) than in the case without tidal mixing. Accordingly, the joint effect of tidally-induced transport and transformation dominating in the Kuril Straits and subsequent eddy-transport is considered to play an important role in the ventilation of both the Okhotsk Sea and the North Pacific Ocean.