Understanding the sources and biogeochemical processes influencing the dissolved iron (DFe) distribution is crucial because of its coupled role in C- and N-fixation in the oceans. Vertical depth profiles of DFe in the northwestern Indian Ocean along two meridional transects (∼65 °E and ∼57 °E) during spring and fall seasons are presented here under the GEOTRACES-INDIA initiative. The DFe in the surface waters exhibited both spatial and seasonal variabilities; N-S gradient with higher values in the north; and notably higher concentrations in the fall season. The photic zone-integrated DFe (57.5 ± 13.4 µmol m) was double in the Arabian Sea compared to the subtropical Indian Ocean (31.81 ± 7.63 µmol m) with a significant positive correlation with the photic zone integrated primary production. This suggests higher availability of DFe is responsible for high primary production in the Arabian Sea compared to the subtropical Indian Ocean. Lateral and vertical advection along with particle dissolution from the atmospheric dust fluxes and scavenging-adsorption processes could play prominent role in controlling photic DFe concentrations in the Arabian Sea. The continental margin sources, redox chemistry, and remineralization are responsible for the observed high DFe concentration within the intense oxygen minimum zone. The in-situ remineralization ratios of Fe to C in the Arabian Sea are higher than any other region of the Indian Ocean. It could be due to the high uptake of Fe during primary production in the Arabian Sea, despite huge spatio-temporal variations in the abundance of phytoplankton communities. Our DFe data from the undersampled region over the Carlsberg Ridge suggests the presence of chronic/event plumes contributing to the DFe inventory in the western Arabian Sea region.

中文翻译：

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阿拉伯海和印度洋副热带环流地区的溶解铁循环

了解影响溶解铁 (DFe) 分布的来源和生物地球化学过程至关重要，因为它在海洋中的碳固定和氮固定中发挥着耦合作用。这里根据 GEOTRACES-INDIA 计划展示了春季和秋季期间印度洋西北部沿两条经向横断面（∼65 °E 和∼57 °E）的 DFe 垂直深度剖面。地表水中的DFe表现出空间和季节变化； NS梯度在北部值较高；秋季的浓度尤其更高。阿拉伯海的透光区综合 DFe (57.5 ± 13.4 µmol m) 是亚热带印度洋 (31.81 ± 7.63 µmol m) 的两倍，与透光区综合初级生产力呈显着正相关。这表明，与亚热带印度洋相比，阿拉伯海的初级生产力较高，因此 DFe 的可用性较高。横向和垂直平流以及大气尘埃通量中的颗粒溶解和清除吸附过程可以在控制阿拉伯海的光 DFe 浓度方面发挥重要作用。大陆边缘来源、氧化还原化学和再矿化是在强氧最低区内观察到的高 DFe 浓度的原因。阿拉伯海铁与碳的原位再矿化比率高于印度洋任何其他地区。这可能是由于阿拉伯海初级生产过程中对铁的大量吸收，尽管浮游植物群落丰度存在巨大的时空变化。我们来自嘉士伯海岭欠采样区域的 DFe 数据表明，存在慢性/事件羽流，对阿拉伯海西部地区的 DFe 库存有贡献。