The Role of Double Diffusive Convection in the Mixing Process in the ocean

1.在西北太平洋海区，2004年和2005年利用CTD和Turburap对温度、盐度和湍流耗散进行了详细的观测，结果表明，在典型水团接触的区域，混合过程的增强可能是由于发生了双扩散对流。特别是在三里库沿岸，观测到了界面具有高湍流耗散率的双扩散交错过程。2.采用简单的一维温度-盐度扩散模式，对垂直涡旋扩散系数随密度比的变化进行了参数化，研究了北大西洋典型观测到的垂直温度和盐度廓线的发展。我们首次成功地证明了由双扩散对流引起的密度流收敛所导致的台阶结构的形成。这些阶跃首先具有较小的垂直尺度，然后合并以增加其厚度，最后接近于密度比为2的平滑的温度和盐度剖面，这种最终状态与观测相吻合。3.继续从WOCE数据集绘制世界海洋的密度比。在本研究过程中，通过双扩散对流的密度通量比来估算垂直涡旋扩散系数。在整个大西洋和南极绕极流附近海域，我们获得了1个Munk(10^&lt；-4；m^2/S)。但在太平洋，这一数值最高为10^&lt；-6；m^2/S~10；-5&gt；m^2/S。这些值不足以维持永久温跃层，但双扩散对流的影响对于这一过程是不可忽略的。

1.In the area of the western-north Pacific ocean, detailed observations of temperature, salinity and turbulent dissipation using CTD and Turbomap in 2004 and 2005 showed enhanced mixing processes might be due to double diffusive convection occurred in the area where typical water masses were contacted. Especially, off the Sanriku coast, double diffusive interleaving processes having high turbulent dissipation rate at the interfaces were observed from Thrbomap yo-yo observation.2.Simple one-dimensional temperature-salinity diffusion model parameterizing the vertical eddy diffusivities changing with density ratio were employed to investigate the development of vertical temperature and salinity profiles typically observed in the north Atlantic. We first successfully showed the formation of step structure caused by the convergence of density flux due to double diffusive convection. These steps having small vertical scale at first, merges to increase their thickness, and finally approaches smooth temperature and salinity profiles with the density ratio value 2. This final state is coincided with the observation.3.Mapping of density ratio in the world ocean from WOCE data set has been continued. In the course of this study, vertical eddy diffusivities are estimated through the density flux ratio due to double diffusive convection. We obtained 1 Munk (10^<-4>m^2/s) in the whole Atlantic Ocean and in the area around Antarctic Circumpolar Current. But, in the Pacific Ocean, the value was 10^<-6>m^2/s〜l0^<-5>m^2/s at most. These latter values are not sufficient to maintain the permanent thermocline, but the effect of double diffusive convection is not negligible for this process.