Seasonal and interannual variabilities of surface and subsurface chlorophyll (Chl) in the eastern equatorial Indian Ocean (IO) and Bay of Bengal were examined based on vertical Chl inferred from satellite data. Four biotic zones were identified by Empirical orthogonal function analysis, which represented different types of mixed layer processes. The areas south of Sri Lanka indicated the most significant Chl increase in the surface and subsurface during summer due to coastal upwelling. Surface Chl highs in the Sri Lanka Dome occurred every summer during the time series. Chl increases were also recorded in the southwestern Bay of Bengal during fall–winter in response to wind-induced divergence and convective mixing. The other two zones in south IO basin between 5 and 15°S exhibited seasonal surface Chl highs in summer and subsurface Chl maximum during fall–winter. Wind-induced divergence plays a major role in the maintenance of this upwelling zone year-round; however, stratification inhibited the surface Chl increase in winter and results in enhanced Chl in the subsurface. The Chl interannual variability was related with Indian Ocean dipole (IOD) associated physical field oscillations. In positive IOD, wind divergence increased significantly along the eastern equatorial IO coast that contributed to Chl enhancement there, it decreased in Bay of Bengal and South IO and acted to reduce the Chl in these regions. In negative IOD, reversals in the forcing anomalies drove increasing Chl in Bay of Bengal and South IO and decreasing of that in the eastern equator. This resulted in significant correlations between IOD index and Chl confined in these regions. There are pronounced variance of phytoplankton carbon biomass in the Bay of Bengal in IOD events, however, less changes of that were seen over the South IO during IOD. Our findings imply that physiological changes in cellular pigmentation are the dominant cause of satellite-observed interannual variations in Chl in the South IO. Our results highlight the role of physiological processes in regulating Chl distributions, and support the use of Chl-based indices as indicators of climatic feedbacks.

基于从卫星数据推断出的垂直 Chl，研究了东赤道印度洋 (IO) 和孟加拉湾的表层和地下叶绿素 (Chl) 的季节性和年际变化。通过经验正交函数分析确定了四个生物区，它们代表了不同类型的混合层过程。由于沿海上升流，斯里兰卡南部地区在夏季地表和地下的 Chl 增加最为显着。在时间序列中，斯里兰卡穹顶的表面 Chl 高点每年夏天都会发生。秋冬季期间，孟加拉湾西南部的 Chl 也因风引起的发散和对流混合而增加。南 IO 盆地的其他两个区域在 5°S 和 15°S 之间在夏季表现出季节性地表 Chl 高值，在秋冬季表现出地下 Chl 最大值。风引起的发散在全年维持这个上升流区中起着重要作用；然而，分层抑制了冬季地表 Chl 的增加，导致地下 Chl 增强。Chl 年际变化与印度洋偶极子 (IOD) 相关的物理场振荡有关。在正 IOD 中，赤道东部 IO 海岸的风散度显着增加，导致那里的 Chl 增强，孟加拉湾和南 IO 的风散度减少，并减少了这些地区的 Chl。在负 IOD 中，强迫异常的逆转导致孟加拉湾和南 IO 的 Chl 增加，而东赤道的 Chl 减少。这导致 IOD 指数与限制在这些区域的 Chl 之间存在显着相关性。孟加拉湾浮游植物碳生物量在 IOD 事件中有明显的变化，然而，在 IOD 期间，南 IO 的变化较小。我们的研究结果表明，细胞色素沉着的生理变化是卫星观测到的南 IO 中 Chl 年际变化的主要原因。我们的结果突出了生理过程在调节 Chl 分布中的作用，并支持使用基于 Chl 的指数作为气候反馈的指标。我们的研究结果表明，细胞色素沉着的生理变化是卫星观测到的南 IO 中 Chl 年际变化的主要原因。我们的结果突出了生理过程在调节 Chl 分布中的作用，并支持使用基于 Chl 的指数作为气候反馈的指标。我们的研究结果表明，细胞色素沉着的生理变化是卫星观测到的南 IO 中 Chl 年际变化的主要原因。我们的结果突出了生理过程在调节 Chl 分布中的作用，并支持使用基于 Chl 的指数作为气候反馈的指标。