Abyssal Circulation Driven by Near-Boundary Mixing: Water Mass Transformations and Interior Stratification
Abyssal Circulation Driven by Near-Boundary Mixing: Water Mass Transformations and Interior Stratification
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DOI：
10.31223/osf.io/djv5h
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发表时间：
2020-01
影响因子：
3.5
通讯作者：
H. Drake;R. Ferrari;J. Callies
中科院分区：
文献类型：
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作者：
H. Drake;R. Ferrari;J. Callies
关于深海环流的新观点是，它与底部增强的混合有关，这种混合导致分层海洋内部的下涌和沿绝缘和倾斜海底的底部边界层的上涌。然而，在缓慢变化的垂直分层和地形的极限下，边界层理论预测，这些上坡和下坡流动在很大程度上进行了补偿，因此沿坡的净水质量变化几乎消失。我们使用行星地转环流模式来解决沿洋中脊底部增强混合的理想盆地的边界层动力学和大规模翻转问题，结果表明，在平衡状态下，分层的垂直变化变得足够大，从而降低了沿洋中脊两侧的补偿程度。由此产生的大净转换与深海的估计相似，并跨越了脊的垂直范围。这些结果表明，混合产生的边界流在设定全球海洋分层和翻转环流方面起着至关重要的作用，需要对深海理论进行修订。
The emerging view of the abyssal circulation is that it is associated with bottom-enhanced mixing, which results in downwelling in the stratified ocean interior and upwelling in a bottom boundary layer along the insulating and sloping seafloor. In the limit of slowly varying vertical stratification and topography, however, boundary layer theory predicts that these upslope and downslope flows largely compensate, such that net water mass transformations along the slope are vanishingly small. Using a planetary geostrophic circulation model that resolves both the boundary layer dynamics and the large-scale overturning in an idealized basin with bottom-enhanced mixing along a midocean ridge, we show that vertical variations in stratification become sufficiently large at equilibrium to reduce the degree of compensation along the midocean ridge flanks. The resulting large net transformations are similar to estimates for the abyssal ocean and span the vertical extent of the ridge. These results suggest that boundary flows generated by mixing play a crucial role in setting the global ocean stratification and overturning circulation, requiring a revision of abyssal ocean theories.