近60年南海盐度多尺度变化过程及其机理研究

The ocean’s salinity field reflects the large scale long-term balance between the surface freshwater flux and the ocean’s advective and mixing processes. Any change in the hydrological cycle, therefore, will be reflected in the ocean salinity field. Multi-scale changes in the ocean’s salinity field have already been reported on global and regional scales. Understanding the long-term salinity variations and underlying mechanisms, especially the signals below the sea surface, is essential to explain the effects of natural variability and climate change on the regional water cycle..The South China Sea (SCS), as an important part of the Indo-Pacific warm pool, is located in between the significant freshening western Pacific Ocean and the Indian Ocean. As part of the Indo-Pacific warm pool, the characteristics of water masses in the largest tropical marginal sea, the SCS, show remarkable open ocean and local properties. The water balance in the SCS is governed mainly by the interplay between vertical mixing, and salt exchange with surrounding oceans and seas..A major impediment to the assessment of long-term salinity changes is the lack of observations, especially below the sea surface where satellites cannot provide data; consequently, the salinity changes in the SCS remains largely unknown. As measurements have become more extensive, large data sets of historical and modern observations can be used to focus on salinity changes in the SCS over the past sixty years. To understand the variations in salinity, we investigate the underlying processes that modify the salinity changes using salinity budget. The salinity budget analysis will be carried out to determine the contributions of each term..The possible outcome of this study that the Salinity changes in the SCS over the past five decades would advance our understanding inconsiderations of the salinity changes in the air-sea interactions and climate forecasts.

海洋水循环是全球水循环的重要组成部分，也是海洋和气候研究的热点和重点科学问题。海洋盐度作为水循环过程的关键可测量因子，是水循环研究的重要指标。全球海洋盐度正发生着显著变化并且各海区表现不同，而南海正处于全球盐度淡化最显著的印太海区之间。南海的盐度特性与邻近大洋有着显著区别，但因资料匮乏，我们对南海盐度变率及其与邻近大洋间联系的认识严重不足。随着南海观测等多源数据的积累，已能支撑我们深入研究南海的盐度变化。本项目以南海盐度多尺度变化及机理为切入点，全面探究近60年南海各海区和深度的极端淡化/盐化事件、年际、年代际和长期变化特征；基于盐度收支诊断，阐明控制南海盐度多尺度变化的关键因子，并进一步探讨南海盐度作为降雨预测因子的可行性，以期为我国气候预测提供新的预测因子。本项目的开展，有助于完善对南海水团特征及变化的认识，为揭示南海区域气候变化及其与邻近大洋间联系提供重要的基础认识。

海洋盐度作为水循环过程的关键可测量因子，是水循环研究的重要指标。而南海的盐度特性与邻近大洋有着显著区别，但因资料匮乏，以往对南海盐度变率及其与邻近大洋间联系的认识严重不足。本项目立足于南海1960-2016年的盐度观测，结合卫星数据、再分析和高分辨率模式数据，通过多种统计检验方法，剖析南海盐度近六十年的多尺度变化特征包括：极端淡化和高盐事件、年际和年代际变化、以及长期变化趋势。基于盐度收支方程，对南海不同深度，如混合层、次表层水团等的盐度变化的影响因子进行判定，并对盐度收支各项进行比较和评估，剖析南海盐度的变化机理和关键影响因子，深入分析了南海盐度多尺度变化受大洋年际/年代际变率的影响。结合涡旋加密观测、物理海洋学数据集、高分辨率海洋模式数据和数值敏感性实验，给出涡致黑潮高盐水输运的观测事实，详细探讨涡致高盐水输运过程的特征并诊断其机制，评估涡平流输运在南海盐度收支中的重要作用。我们研究了涡致黑潮高盐水输运特征与机制，量化评估了其对平流盐输运的贡献。我们逐步展开了对南海盐度作为中国陆地降雨预测因子可行性的探索。我们发现南海中部的春季盐度可以很好的预测中国长江流域和华南地区的夏季降雨，这将推动申报单位在南海中部的盐度观测，对中国陆地降雨的预测有重要意义。