海洋温盐台阶的机理及在北冰洋上层海洋作用的研究

The areas of sea ice have been largely reduced in the Arctic Ocean. Where the heat for melting ice comes from receive much attention. The warm and salty Atlantic Water (AW) lies in the intermediate layer of Arctic Ocean. If the heat in AW were able to reach the sea surface, it is large enough to melt all ice within few years. There are stacks of thermohaline staircases overlying the AW, which are the key structures to understand the heat and salt fluxes and ocean mixing in the upper Arctic Ocean. In this project, we would explore the influences of staircases in the upper Arctic Ocean by analyzing the in situ observational data and by doing laboratory experiments. With in situ observational data and the new method for identify the staircase, the spatial temporal evolution of individual staircase can be well exhibited; By using precision measurements in the laboratory experiments, the parameterizations would be updated to describe the heat and salt transport and turbulent mixing of staircases. With new parameterizations, we will evaluate the role of staircases in the heat and salt fluxes, and ocean mixing in the upper Arctic Ocean. The outcome of this project will broaden the understanding of water mass transport in the Arctic Ocean, which helps us to learn the influence of ocean to the ice-melting.

北冰洋冰层覆盖率持续降低，冰层融化需要的热量来源引起人们关注。北冰洋中层内暖而咸的大西洋水团在逐年增温，如果其热量全部传输到海洋上层，足以融化所有海冰。大西洋水团之上一定深度范围内存在一系列温盐台阶结构。全面认识这些温盐台阶是了解北冰洋上层海洋热盐输运和海洋混合的关键。本项目拟结合机理研究和现场观测，深入探讨温盐台阶在北冰洋上层海洋中的作用。利用北冰洋观测数据和新的台阶确定方法，清晰描述温盐台阶结构的空间和时间演化过程。利用室内流体力学实验和高精度测量技术，确定热、盐通量规律和动力过程规律，优化扩散对流温盐台阶的参数化方案。利用新的成果，准确评估温盐台阶对北冰洋的热、盐通量输运，海洋混合，以及深水形成的影响，进而更全面认识北冰洋水体和海冰变化对全球热盐环流和气候变化的影响。

通过本项目的资助，开展了一系列温盐台阶及小尺度结构的机理研究。利用室内流体力学实验和高精度测量技术，清晰描述温盐台阶结构的空间和时间演化过程。结合全全球温盐台阶的现场观测，优化扩散对流温盐台阶厚度和热通量的参数化方案。通过大量的现场观测数据和室内实验，发现密度比是温盐台阶中重要的参数，台阶的厚度和热通量均是密度比的指数函数。新的厚度参数化方案能够准确描述几厘米（室内实验）到近千米厚（北冰洋底层）的温盐台阶。新的热输运参数化方案对准确评估温盐台阶对北冰洋的热、盐通量输运和海洋混合的影响非常重要。这些参数化方案应用于海洋模式，有助于得到更接近真实的海洋模拟和预测。另外，提出新的确定混合层厚度的方法：相对变化法。相比于现有方法，相对变化法可以更精确确定混合层厚度，这对于研究混合层内的动力，生态和物质变化至关重要。通过本项目的资助，发表SCI论文11篇和培养了研究生4名。