The role of turbulent mixing in the modified Shelf Water overflows that produce Cape Darnley Bottom Water
The role of turbulent mixing in the modified Shelf Water overflows that produce Cape Darnley Bottom Water
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DOI：
10.1002/2014jc010059
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发表时间：
2015-02-01
影响因子：
3.6
通讯作者：
Fukamachi, Yasushi
中科院分区：
文献类型：
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作者：
Hirano, Daisuke;Kitade, Yujiro;Fukamachi, Yasushi
2009年1月，通过水文和微结构观测，研究了与修饰陆架水(MSW)溢流相关的混合过程，最终形成达恩利角底层水(CDBW)。近距离的微观结构观察表明，在沿陆架边缘大约4公里的距离内，城市生活垃圾的性质变化很大。在底层附近，湍流动能耗散率增强到大于1027W·kg(-1)，底层边界层垂直尺度约为10m，观测到的陆架边缘边界层具有强烈的垂直混合特征，湍流涡散系数接近O(102321022)m(2)S(-1)。陆架上空MSW产生的地地平衡的密度流被认为是边界层湍流混合的主要能量来源。这种湍流混合通过与周围水团，特别是与上面修改的环极深水混合，改变了溢出的城市生活垃圾。BBL也被认为在一定程度上促进了城市生活垃圾通过埃克曼底部的运输从大陆斜坡上逐渐下降。我们的结论是，主要由密度流引起的湍流混合对CDBW的形成起着重要的作用，它改变了从CDP溢出的MSW。
The mixing process associated with modified Shelf Water (mSW) overflows that eventually mix to form Cape Darnley Bottom Water (CDBW) was investigated by hydrographic and microstructure observations off the Cape Darnley Polynya (CDP), East Antarctica, in January 2009. Closely spaced microstructure observations revealed that mSW properties varied considerably within a distance of similar to 4 km across the shelf edge. Near the bottom, the rate of turbulent kinetic energy dissipation was enhanced to values greater than 1027 W kg(-1), and the vertical scale of the bottom boundary layer (BBL) was on the order of 10 m. The observed BBL around the shelf edge was characterized by strong vertical mixing with turbulent eddy diffusivities of similar to O(102321022) m(2) s(-1). A geostrophically balanced density current, which resulted from the presence of mSW over the continental shelf, is considered the primary energy source for the turbulent mixing in the BBL. This turbulent mixing transforms the overflowing mSW through mixing with ambient water masses, specifically with the overlying modified Circumpolar Deep Water. The BBL is also thought to partly contribute to the gradual descent of mSW down the continental slope through bottom Ekman transport. We conclude that turbulent mixing, primarily caused by a density current, plays an important role in CDBW formation, by modifying the mSW overflowing from the CDP.