扩散对流台阶结构垂向热盐通量参数化的实验研究

Diffusive-convection (DC) staircases occur commonly in the polar seas with basin scale horizontally. The DC staircases are located between the subsurface warm and salty water masses and the surface cold and fresh ones near the sea ice. The heat and salinity transfer-laws of DC are the basis for understanding heat and salinity transfer from the subsurface warm and salty water masses to the sea ice. In this proposal the DC experiments will be conducted with modern advanced measuring technique of fluid mechanics, and the effect of temperature difference and density ratio on DC heat and salinity transfer will be explored. A new universal parameterization will be proposed for larger density-ratio range, and further verified with recent DC observational dataset in Arctic Ocean. The new parameterization could improve the defects of existing ones, such as small applicable parameter range and large differences with observational dataset, and also could be applied in ocean models to improve their simulation capacity.

扩散对流温盐台阶结构是发生在极地等海域具有海盆尺度的一种常见的海洋现象，它处于次表层高温高盐水和表层接近海冰的低温低盐水之间，因此，准确量化扩散对流热盐输运的基本规律，是理解次表层高温高盐水向表层进行热盐输送的基础。本项目拟采用现代先进的流体力学测量技术，开展温盐扩散对流室内实验，研究温度差、密度比等变量对扩散对流垂向热盐输运的影响规律；通过控制实验条件，提出新的在更大的参数范围内普适的扩散对流热盐通量参数化方案，并通过北冰洋扩散对流观测数据进行验证。预期新的参数化方案可改进现有的方案适用的参数范围小、与最新的大部分海域观测结果差异大等缺陷；并可应用于海洋模式，提高模式模拟能力。

在本项目的资助下，开展了一系列扩散对流温盐台阶的热力学和动力学研究。通过室内地球流体力学实验，严格控制初始和边界条件，测量了扩散对流温盐台阶的垂向热盐输运，提出了在大的密度比范围内普适的扩散对流垂向热盐通量参数化方案，并通过海洋现场观测数据对该方案进行了验证和应用。该方案对于准确评估北冰洋上层热输运及其对海冰和气候变化有重要意义，并可以对现有的海洋模式进行修正以提高模拟和预测能力。进一步，基于扩散对流温盐台阶结构的界面-混合层结构特征，提出新的确定海洋底混合层厚度的方法-“集合法”。应用该方法评估了全球海洋底混合层厚度及其空间分布，以及南海北部底混合层内对流不稳定对底层湍流混合的贡献。以上研究成果共发表论文11篇，其中SCI论文8篇；申请专利5项，其中已授权4项。