黄海风生近惯性内波生消机制及其对跃层湍流混合影响研究

The wind-induced near-inertial wave (NIW) is a ubiquitous phenomenon in the world ocean. It remains itself as a key mechanism for the wind to inject energy into the ocean interior. The interior mixing that caused by the inertial shear is thought to be an important energy source which drives the exchange of momentum, heat, and various substances in the ocean. Thus, investigations of the NIW and their associated mixing results are research frontiers in physical oceanography. The Yellow Sea (YS) is easy to be influenced by the NIW. By now, most researches have been focused on describing features of the wind-induced NIW in the YS. In comparison, mechanisms underlying the changing NIW and their impacts on the interior mixing are still not well understood. Based on a combination of long-term mooring observations, multi-year turbulence profiling measurements, theoretical analyses and numerical modeling, this project aim to explore (i) the varying feature and underlying mechanisms of wind-induced NIW in the YS, the key processes that influence the variation of NIW and the associated vertical modal structure, (ii) the impact of the generated inertial shear on the YS mid-column mixing, the turbulent mixing generation mechanisms that occurring in the pycnocline. Interior mixing in the ocean directly drives the diapycnal exchange of heat, nutrients, and dissolved oxygen. This study will thus provide the important theoretical foundation for better understanding the seasonal evolution of YS cold water mass and scientifically evaluating the YS carrying ability.

风生近惯性内波（Near-inertial wave, NIW）几乎在全球海洋中都存在，它是风向海洋内部输入能量的重要通道，产生的近惯性剪切对海洋内部湍流混合以及动量、热量、物质交换具有重要影响，因此不同海域NIW的生消机制与混合效应是物理海洋研究的前沿。黄海是NIW的多发海区，现有研究大多仅描述黄海风生NIW的特征，尚无对NIW能量从强迫生成到最终耗散影响水体混合的系统认识。本项目拟利用黄海长期潜标流速剖面与多年大面湍流剖面等观测资料，结合理论分析与数值模拟，分析风生NIW的变化规律，揭示控制NIW生消过程、垂向模态演变特征的关键因素与机制；衡量近惯性剪切对于黄海内部湍流混合贡献，阐明跃层湍流混合的生成机制，深化对NIW能量耗散影响跃层混合这一过程的认识。海洋内部湍流混合驱动着热量、营养盐与溶解氧等跨等密面输运，本研究可为认识黄海冷水团季节变化、科学评估海洋养殖容量等提供重要理论基础。

风生近惯性内波的激发、演变与耗散过程是连接海洋大尺度能量源与小尺度湍流混合的重要能量传输通道，是物理海洋学的前沿科学问题，对于认识整个海洋的能量传递、物质循环等具有重要意义。本项目基于大量现场流速与微尺度剖面的直接观测资料，结合理论分析与风驱模型等，研究了黄海近惯性内波生消演变与湍流混合的特征和机制，取得了以下成果：（1）黄海近惯性内波呈现显著的夏强冬弱的季节变化特征，这一方面是受层结季节变化的调制，另一方面夏季黄海频繁过境的副热带气旋系统也起了重要作用，此外，风场与已生成的近惯性内波存在持续相互作用，这一作用机制导致了跃层间歇性强剪切的出现。（2）创新性地发现了夏季黄海中部存在普遍的跃层强湍流现象，这一中层强湍流现象主要发生在中层低盐水层的上边界，这一深度可能有盐指现象存在，进一步探讨了盐指与近惯性剪切相互作用造成跃层强湍流的可能性，并对黄海中层低盐水的存在特征与生态效应进行了定量研究。（3）系统研究了内潮与内孤立波等其它类型内波对黄海跃层湍流混合的影响，验证了陆架海跃层湍流参数化模型的适用性，量化了内波对垂向营养盐和盐度输运的跨量级提升作用。基于项目研究成果，目前已发表7篇SCI论文，研究成果深化了对陆架海近惯性内波生消机理与跃层湍流混合机制的认识，提升了对黄海跨跃层垂向输运的理解，为提升陆架海湍流混合参数化方案表现和完整认识黄海生态系统提供了科学基础。