The role of double diffusive convection on the mixing processes in the ocean

利用WOCE资料，通过全球密度比分布研究了双扩散对流的活动性。总的来说，大约43%的海洋层是有利于双扩散对流的爆发，这表明在全球海洋环流和水团改造过程中的重要作用。与Levitus气候资料的结果进行了比较，并与流域尺度分布相吻合。通过对Oyashio区至黑潮延伸区的中性面分析和湍流混合分析，揭示了cabbeling和盐指对流在北太平洋中层水（NPIW）改造过程中的重要作用。结果表明，Oyashio冬季混合层水（26.65σθ）比NPIW的盐度最低值（26.80σθ）对较轻层的增鲜作用更强，但不能通过成缆和双扩散对流而成为NPIW的盐度最低值。

The activity of double diffusive convection was investigated through the global density ratio distribution using the WOCE data set. In total, about 43% of the oceanic layers are favorable for the onset of double diffusive convectin, suggesting the important role on the global ocean circulation and the water mass modification processes. Our results are compared with those obtained from the Levitus climatological data set, and was coincided with the basin scale distribution. However, as for the sharp oceanic frontal area which are usually smoothed out from the Levitus data set, our results showed the possibility of high activity of double diffusive convection.Neutral surface analysis and turbulent mixing analysis were applied for the Oyashio region to the Kuroshio Extension, which reveals the important role of cabbeling and salt finger convection to the modification process of the Northa Pacific Intermediate Water(NPIW). It is concluded that the Oyashio winter mixed layer water (26.65σθ) contributes to the freshening of the lighter layer than the salinity minimum of the NPIW (26.80σθ) and could not become the salinity minimum of the NPIW by the cabbeling and the double diffusive convection.