The thickness of oxygen minimum zone (OMZ) is estimated for the first time using dissolved oxygen (DO) profiles obtained from the Biogeochemical Argo floats collected between 2013 and 2019 in the Arabian Sea. The depth of upper boundary of the OMZ varied narrowly between 70 and 220 m in the entire Arabian Sea whereas the lower boundary of OMZ significantly deepened from south (500 m) to northern Arabian Sea (1200 m). The thickness of OMZ decreased from north (>1050 m) to south (400 m) with the thickest OMZ in the northeastern Arabian Sea (950–1050 m). The thick OMZ in the northeastern Arabian Sea is associated with low concentration of depth integrated Chlorophyll-a, primary production in the upper 100 m and sinking carbon fluxes at 100 m depth than other regions. The particle back-scatter, proxy for particulate organic matter, is higher in the northeastern than other regions in the Arabian Sea. The high particle back-scatter data is found in the core of OMZ and it is increased from shelf to offshore indicating that cross-shelf transport of organic matter may be supporting bacterial carbon demand in the OMZ in the northeastern Arabian Sea. The eastward shift in the OMZ is attributed to weak mixing, high penetration time of intermediate water masses, and organic matter transport from the shelf region. Numerical models estimated negligible changes in DO in the OMZ since past several decades, whereas long-term observational data indicates decline in DO levels in the OMZ. Such contrasting results may be caused by lack of cross-shelf transport of organic matter in the models. Though this study identifies the occurrence of cross-shelf transport, the nature, quality and composition of organic matter transported from shelf is unknown. Nevertheless, inclusion of such processes in the models may improve predictability of possible changes in OMZ in future in the Arabian Sea.

首次使用从2013年至2019年在阿拉伯海收集的生物地球化学Argo浮标获得的溶解氧（DO）曲线首次估算了最低氧区域（OMZ）的厚度。在整个阿拉伯海中，OMZ的上边界深度在70至220 m之间狭窄地变化，而OMZ的下边界从南部（500 m）到北部阿拉伯海（1200 m）显着加深。OMZ的厚度从北部（> 1050 m）减小到南部（400 m），而阿拉伯东北部的OMZ厚度最大（950-1050 m）。阿拉伯海东北部厚的OMZ与深度整合的叶绿素-a浓度低，上部100 m的初级产量和100m深度的碳通量下沉比其他地区低有关。粒子反向散射，替代了颗粒有机物，东北地区比阿拉伯海其他地区更高。在OMZ的核心发现了高粒子反向散射数据，并且该数据从架子到近海增加，这表明有机物的跨层运输可能支持阿拉伯海东北部OMZ中的细菌碳需求。OMZ的东移归因于混合力弱，中间水团的渗透时间长以及有机物从陆架区的迁移。数值模型估计过去几十年来OMZ中DO的变化可忽略不计，而长期的观测数据表明OMZ中DO含量下降。这种对比结果可能是由于模型中缺乏有机物的跨架运输所致。尽管这项研究确定了跨架运输的发生，但是自然界，从架子运来的有机物的质量和成分尚不清楚。但是，将这些过程包括在模型中可能会提高未来阿拉伯海OMZ可能变化的可预测性。