南大洋印度洋扇区南极底层水的形成过程及生成量估算研究

New Antarctic Bottom Water (AABW) formation regions have been discovered by recent mooring observations. Different trends of water warming and freshening around Antarctica have also been detected by long-term hydrographic observations. However, the detailed physical mechanisms during AABW formation, and their impact on AABW production have not been clarified unambiguously. Therefore, it’s necessary to incorporate newest observation results to study the formation of AABW, which includes the production rates, the detailed physical mechanisms during AABW formation. In this project, based on the highly targeted observation data obtained near two AABW formation regions in the Indian sector of the Southern Ocean during 2010-2013, we analyze the physical mechanisms associated with AABW formation and estimate the production rates. We also attempt to provide a proper calculation method for heat/salt flux estimations, and clarify the effects of turbulent mixing, double-diffusive convection and surface cooling, respectively. This research will promote the understanding on AABW formation and its modification, provide references for further study on the global Meridional Overturning Circulation.

近年来通过锚碇观测，在南极大陆周边陆续发现了新的南极底层水生成源地。长期现场观测也确定了南极周边海域各地水团出现不同程度暖化淡化的变异趋势。然而，底层水生成过程中涉及的具体物理机制及其对底层水生成量的影响却尚不清楚。因此，有必要结合最新的观测研究成果，对南极底层水的生成，主要包括其生成量、形成过程中涉及的物理机制，进行准确估算分析。本项目通过分析2010-2013年度在南大洋印度洋扇区内两个南极底层水生成源地附近采集的多样现场观测数据，开展南极底层水形成过程中具体物理机制和生成量估算的研究，提出适当的热/盐通量测算方法，研究在两通量中湍流混合、重扩散对流、海面冷却等各自的作用。通过本项目研究，将促进对底层水生成和变异的理解，为进一步开展全球经向翻转环流研究提供科学参考依据。

近年来通过锚碇观测，在南极大陆周边陆续发现了新的南极底层水生成源地。长期水文观测也确定了南极周边海域各地水团出现不同程度暖化淡化的变异趋势。然而，底层水生成过程中涉及的具体物理机制及其对底层水生成量的影响却尚不清楚。因此，本项目主要根据高质量现场观测数据，对南极底层水生成过程中涉及的物理机制，及其淡化/暖化现象进行了定量研究。由于南极底层水是高密度陆架水和绕极深层水混合下沉的结果，因此本项目从高密度陆架水的生成和海水混合两方面开展研究。结果显示，高密度陆架水出现三个阶段的温盐特性演变；在3-4月期间持续冷却的外部强迫下，双扩散对流中的“扩散对流”混合形式占陆架上整个水柱的50%以上，对高密度陆架水的生成起到关键作用；文生湾底层水可能对南极底层水的淡化有贡献，在文生湾前缘其影响到达海底，呈现区域变化性和年际变化性。并且发现，其贡献在在南极底层水的中层淡化趋势中不可忽视。