The central Arabian Sea (CAS) is productive during both the summer and winter monsoons owing to different physical processes. We analysed four years (2013–2016) record of chlorophyll and dissolved oxygen (DO) concentration from a Bio-Argo float deployed in this region. Though the surface blooms were observed during both the monsoons and sub-surface chlorophyll was also persistently observed, the intensity and duration of the bloom have been decreasing over the past few years. Also, the winter blooms were more prominent compared to the summer bloom in the study region. Our analysis shows that the observed inter-annual variability in the summer bloom can be attributed to the variability in wind speed, oceanic stratification and advection of nutrient rich water from the western Arabian Sea. During both the monsoons, stratification played an important role in reducing the productivity in recent years. We also found that during the winter monsoon, the upwelling Rossby wave propagating from the west coast of India influenced productivity as north as 15°N. The chlorophyll data from Bio-Argo float shows that the total surface chlorophyll concentration and backscattering (a proxy for particulate flux) in the OMZ region have been decreasing during the study period. Consequently, the DO concentration in the deeper waters has also been increasing. We believe that the decrease in surface productivity, lateral advection from the west and their manifestation on the export flux has reduced the oxygen demand in the deeper layer.

由于不同的物理过程，阿拉伯海中部（CAS）在夏季和冬季季风期间均富饶。我们分析了四年（2013-2016年）从部署在该区域的Bio-Argo浮游生物中的叶绿素和溶解氧（DO）浓度的记录。尽管在季风期间都观察到表面开花，并且还持续观察到亚表层叶绿素，但在过去几年中，开花的强度和持续时间一直在减少。此外，与研究地区的夏季花朵相比，冬季花朵更显着。我们的分析表明，夏季开花期间观测到的年际变化可归因于阿拉伯海西部风速，海洋分层和对流养分丰富的水的平流性。在两个季风中 近年来，分层在降低生产率方面发挥了重要作用。我们还发现，在冬季季风期间，从印度西海岸传播的上升的Rossby波影响了北至15°N的生产力。来自Bio-Argo浮游生物的叶绿素数据表明，在研究期间，OMZ区的总表面叶绿素浓度和反向散射（代表颗粒通量）一直在下降。因此，深水中的溶解氧浓度也一直在增加。我们认为，地表生产力的下降，西部的对流平流及其在出口通量上的表现降低了较深层的需氧量。从印度西海岸传播的上升的罗斯比波影响了北向15°N的生产率。来自Bio-Argo浮游生物的叶绿素数据表明，在研究期间，OMZ区的总表面叶绿素浓度和反向散射（代表颗粒通量）一直在下降。因此，深水中的溶解氧浓度也一直在增加。我们认为，地表生产力的下降，西部的对流平流及其在出口通量上的表现降低了较深层的需氧量。从印度西海岸传播的上升的罗斯比波影响了北向15°N的生产率。来自Bio-Argo浮游生物的叶绿素数据表明，在研究期间，OMZ区的总表面叶绿素浓度和反向散射（代表颗粒通量）一直在下降。因此，深水中的溶解氧浓度也一直在增加。我们认为，地表生产力的下降，西部的对流平流及其在出口通量上的表现降低了较深层的需氧量。因此，深水中的溶解氧浓度也一直在增加。我们认为，地表生产力的下降，西部的对流平流及其在出口通量上的表现降低了较深层的需氧量。因此，深水中的溶解氧浓度也一直在增加。我们认为，地表生产力的下降，西部的对流平流及其在出口通量上的表现降低了较深层的需氧量。