Interior Water-Mass Variability in the Southern Hemisphere Oceans during the Last Decade
Interior Water-Mass Variability in the Southern Hemisphere Oceans during the Last Decade
复制标题
DOI：
10.1175/jpo-d-19-0128.1
复制
发表时间：
2020-02
影响因子：
3.5
通讯作者：
E. Portela;N. Kolodziejczyk;C. Maes;V. Thierry
中科院分区：
文献类型：
--
作者：
E. Portela;N. Kolodziejczyk;C. Maes;V. Thierry
使用Argo数据集和ECCOv 4再分析，进行了体积预算，以解决2006年至2015年南半球海洋内部水团体积变化的主要机制。在密度-辛度（σ-τ）框架下估算了俯冲速率和等密度水团与穿密度水团的转换。辣味，定义为温盐变化沿着isopycnals，被添加到潜在的密度坐标，以区分水团传播等密度层。发现主要的正体积趋势与南太平洋和南印度洋海盆的亚季风沃茨（SAMW）有关，揭示了南半球上层沃茨的减轻。SAMW具有两层密度结构，其中俯冲和从下层到上层的diapycnal转换分别占上层体积增加和下层体积损失的大部分。南极中间沃茨，在这里被定义为27.2和27.5 kg m−3等密度线之间，表现出最强的负体积趋势。这种体积损失可以解释为它们的负等压面转换南极绕极流南到新鲜和寒冷的南极冬季沃茨（AAWW）和北到辛辣的热带/亚热带中间沃茨。AAWW被逆冲作用破坏，返回混合层，因此其净体积变化几乎保持为零。在南大洋动力学的背景下，讨论了解释中间沃茨内变化的拟议机制。σ-τ分解为过去十年水团的时空变化和驱动机制提供了新的见解。
Using an Argo dataset and the ECCOv4 reanalysis, a volume budget was performed to address the main mechanisms driving the volume change of the interior water masses in the Southern Hemisphere oceans between 2006 and 2015. The subduction rates and the isopycnal and diapycnal water-mass transformation were estimated in a density–spiciness (σ–τ) framework. Spiciness, defined as thermohaline variations along isopycnals, was added to the potential density coordinates to discriminate between water masses spreading on isopycnal layers. The main positive volume trends were found to be associated with the Subantarctic Mode Waters (SAMW) in the South Pacific and South Indian Ocean basins, revealing a lightening of the upper waters in the Southern Hemisphere. The SAMW exhibits a two-layer density structure in which subduction and diapycnal transformation from the lower to the upper layers accounted for most of the upper-layer volume gain and lower-layer volume loss, respectively. The Antarctic Intermediate Waters, defined here between the 27.2 and 27.5 kg m−3 isopycnals, showed the strongest negative volume trends. This volume loss can be explained by their negative isopyncal transformation southward of the Antarctic Circumpolar Current into the fresher and colder Antarctic Winter Waters (AAWW) and northward into spicier tropical/subtropical Intermediate Waters. The AAWW is destroyed by obduction back into the mixed layer so that its net volume change remains nearly zero. The proposed mechanisms to explain the transformation within the Intermediate Waters are discussed in the context of Southern Ocean dynamics. The σ–τ decomposition provided new insight on the spatial and temporal water-mass variability and driving mechanisms over the last decade.