全球变暖背景下黑潮和亲潮延伸体的低频变率特征及机理研究

Variability and dynamics of the western boundary currents and their extensions are among the most important issues in physical oceanography. It is observed that both Kuroshio Extension (KE) and Oyashio Extension (OE) show significant low-frequency variations (LFV) on interannual to decadal time scales, which have a profound impact on the mid-latitude large-scale atmospheric circulations, oceanic dynamical properties and marine ecosystems in the North Pacific. Previous studies mainly focus on the linear trend or the changes of their mean states in the research of responses of the KE and OE to global warming. However, the period, intensity, etc. of their LFV, have not been emphasized due to lack of long-term observations and high resolution coupled models. This planned research will combine multiple observations, CMIP6 eddy-permitting resolution multi-model outputs and reduced-gravity model experiments, to study the low-frequency variabilities of the KE and OE under global warming. From the aspects of wind stress forcing and oceanic adjustment, this study will investigate the key dynamical and thermodynamical processes contributing to their LFV. Meanwhile, dynamical links between the KE and OE will also be addressed, as well as the corresponding mechanisms. This study will not only help to better understand the future changes and dynamics of the mid-latitude western boundary current system, but also provide some basis for the climate predictions and fishery productions in the North Pacific.

西边界流及其延伸体环流变异和机理研究是物理海洋前沿热点之一。观测表明黑潮和亲潮延伸体在年际至年代际时间尺度上都存在显著的低频变异，对北太平洋中纬度大气环流、海洋动力环境以及海洋生态系统具有重要的影响作用。对于黑潮和亲潮延伸体在全球变暖背景下的响应研究，前人多关注于线性趋势或平均态差异，而两者低频变异的周期、强度等特征，由于缺乏长期观测资料以及高分辨率耦合模式仍缺少研究。本项目拟结合多种观测资料、CMIP6涡旋相容分辨率的多模式输出结果以及约化重力模型实验，揭示全球变暖背景下黑潮和亲潮延伸体各自的低频变率特征，从外部风场强迫和海洋内部调整等方面阐明影响两者低频变异的关键动力及热力过程，同时研究两者之间的动力联系及物理机制。本项目将有助于提高对中纬度西边界流系统未来变化和变异机理的认知，并为北太平洋气候预测及渔业生产提供理论依据。

黑潮-亲潮延伸体在年际至年代际时间尺度上存在显著的低频变异，对北太平洋中纬度大气环流、海洋动力环境以及海洋生态系统具有重要的影响作用。本项目基于CMIP5多模式集合实验和约化重力模型，分析了黑潮-亲潮延伸体在未来增暖情景下的低频变率特征，发现随着全球增暖的不断发展，上层海洋层结加强，一阶斜压Rossby波加速，进而导致黑潮-亲潮延伸体区域海洋调整周期缩短，因此黑潮-亲潮延伸体低频变率趋向高频发展。此外通过分析Argo格点化资料，本项目研究了本世纪初期全球变暖减缓期间，包括黑潮-亲潮延伸体区域在内的全球海洋主要储热区域的热含量趋势特征，发现其与内区经向输运的趋势具有很好的相关性，揭示了内区经向地转输运变化对海洋年代际储热及放热过程的调制作用。本项目研究成果有助于提高对中纬度西边界流系统未来变化和变异机理的认知，并为北太平洋气候预测及渔业生产提供理论依据。