ABSTRACT This study investigates the interannual variability of the surface and subsurface Chlorophyll-a Concentration (CC) over the Sri Lankan Dome (SLD) in the Bay of Bengal (BoB) and its possible linkages to local wind-induced upwelling and advection-driven CC transport via southwest monsoon current (SMC) from surrounding waters. A regional ocean modelling system (ROMS) coupled with a nitrogen-based nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model has been used to simulate the three-dimensional SMC and the upwelling system over the SLD region (5–10 N, 82–87 E) during 2003–2016. A deep chlorophyll maximum (DCM: 0.8–1.8 mg m−3) is observed at the intermediate depths of 10 to 55 m. The model-simulated CC in the SLD region shows a seasonal variation with maximum value during June through September (JJAS), compares well with Bio-Argo observations available nearby, and significantly correlates (r = 0.78) with satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS). The subsurface chlorophyll distribution demonstrated strong interannual variability, especially during JJAS and is associated with concurrent upwelling. The Ekman Pumping correlates well with the thermocline depth (r = −0.70) and with the deep chlorophyll maximum (r = −0.74). The simulated zonal transport of chlorophyll across 80 E is moderately correlated with the surface chlorophyll on SLD from MODIS observation (0.69) and from the biophysical simulation (0.79), which signifies the role of SMC intrusion from the Arabian Sea to the southwestern BoB. A data-model composite analysis showed that a favourable wind stress curl and shallower thermocline enhanced the Chlorophyll concentration in the SLD region in the high-chlorophyll years (2004, 2014, and 2016). In contrast, reduced advection from the Arabian Sea, deeper thermocline, and the weakening of the deep chlorophyll maxima are responsible for lowering the chlorophyll concentration during the low-chlorophyll years (2008, 2009, and 2011).

中文翻译：

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孟加拉湾斯里兰卡穹顶上叶绿素-a 浓度的年际变化

摘要 本研究调查了孟加拉湾 (BoB) 斯里兰卡穹顶 (SLD) 的地表和地下叶绿素-a 浓度 (CC) 的年际变化及其与当地风引起的上升流和平流驱动的 CC 的可能联系通过西南季风流（SMC）从周围水域运输。区域海洋建模系统 (ROMS) 加上氮基营养物、浮游植物、浮游动物和碎屑 (NPZD) 生态系统模型已被用于模拟三维 SMC 和 SLD 区域（5-10 N , 82-87 E) 在 2003-2016 年期间。在 10 至 55 m 的中间深度处观察到深叶绿素最大值（DCM：0.8-1.8 mg m-3）。SLD 地区模型模拟的 CC 显示出季节性变化，在 6 月至 9 月期间具有最大值（JJAS），与附近可用的 Bio-Argo 观测结果相比较，并且与来自中分辨率成像光谱仪 (MODIS) 的卫星观测结果显着相关 (r = 0.78)。地下叶绿素分布表现出强烈的年际变化，特别是在 JJAS 期间，并且与同时上升流有关。Ekman Pumping 与温跃层深度 (r = -0.70) 和深层叶绿素最大值 (r = -0.74) 密切相关。MODIS观测（0.69）和生物物理模拟（0.79）中模拟的叶绿素在80 E的带状运输与SLD的表面叶绿素中等相关，这表明SMC从阿拉伯海侵入BoB西南部的作用。数据模型综合分析表明，在高叶绿素年（2004、2014 和 2016 年），有利的风应力卷曲和较浅的温跃层提高了 SLD 地区的叶绿素浓度。相比之下，来自阿拉伯海的平流减少、更深的温跃层和深叶绿素最大值的减弱是导致叶绿素含量低的年份（2008、2009 和 2011 年）叶绿素浓度降低的原因。