Dissolved aluminium (dAl) distribution has been studied over the full vertical water column profiles along the GEOTRACES-India (GI) transect, GI-05, in the Arabian Sea (AS) and the Western Equatorial Indian Ocean (W-Eq.IO) during the fall inter-monsoon period. Surface dAl distribution in the AS demonstrates an east-west gradient, i.e., elevated dAl (6.5–21.6 nM) close to the Indian coastal region and low dAl (1.5–3.6 nM) along the western boundary of the AS. Rapid surface dAl removal due to relatively high biological productivity and a decrease in atmospheric dust deposition during the fall inter-monsoon result in low surface dAl levels in the western AS. Mass balance for surface dAl variation in the AS reveals very short scavenging removal timescales (0.01–0.47 yr) between the mid-summer and fall inter-monsoon period. Further, dAl input/dilution due to surface water advection is found to play an important role in controlling the surface dAl variation, varying between 190 and 300% of the dust-supported dAl input in different regions of the AS. These results have important implications for the use of surface dAl as a proxy of dust deposition in the AS. In the W-Eq.IO, a relative increase observed in the surface dAl concentrations, compared to the western AS and the central equatorial region, suggests a local dAl input, presumably, due to the dust influx from the Somali coast. Probable mechanism for this could be dust input from Somalia to the coastal western equatorial region and subsequent advection of the dAl enriched coastal waters to the offshore sampling sites, facilitated by mesoscale eddies.

The intrusions of the high salinity water masses (the Arabian Sea High Salinity Water and the Persian Gulf Water) in the thermocline depths (~75–300 m) are observed to carry the dAl-rich signal of their formation regions to the open AS. This dAl enrichment in thermocline waters is, however, mostly restricted to the northern and north-western AS during the study period. Correlated dissolved Al and Fe maxima observed in the deep water over the Murray Ridge in the northern AS suggest Al and Fe release from reactive clay minerals (e.g., illite), found abundantly in the sediments deposited over the ridge. Further, elevated dAl levels were also seen near the Laxmi-Panikkar-Palitana ridge system (~10.0 nM) and the Carlsberg Ridge (~4.5 nM) in the AS and the W-Eq.IO, respectively.

已经研究了阿拉伯海 (AS) 和西赤道印度洋 (W-Eq.IO) 沿 GEOTRACES-印度 (GI) 样带 GI-05 的完整垂直水柱剖面上的溶解铝 (dAl) 分布在秋季的季风间期。AS中的表面dAl分布表现出东西梯度，即靠近印度沿海地区的dAl升高（6.5-21.6 nM），而沿AS西部边界的dAl低（1.5-3.6 nM）。由于相对较高的生物生产力和秋季季风期间大气尘埃沉积的减少，地表 dAl 的快速去除导致西部 AS 的地表 dAl 水平较低。AS 中地表 dAl 变化的质量平衡表明，夏季中期和秋季季风间期之间的清除清除时间尺度非常短（0.01-0.47 年）。更远，发现由于地表水平流导致的 dAl 输入/稀释在控制地表 dAl 变化中起重要作用，在 AS 不同区域的尘埃支持的 dAl 输入的 190% 到 300% 之间变化。这些结果对于使用表面 dAl 作为 AS 中灰尘沉积的代表具有重要意义。在 W-Eq.IO 中，与西部 AS 和中部相比，观察到表面 dAl 浓度的相对增加赤道地区，表明当地的 dAl 输入，大概是由于来自索马里海岸的沙尘流入。造成这种情况的可能机制可能是从索马里进入赤道西部沿海地区的灰尘输入，以及随后在中尺度涡流的促进下，富含 dAl 的沿海水域平流到近海采样点。

观察到高盐度水团（阿拉伯海高盐度水和波斯湾水）在温跃层深度（~75-300 m）的入侵，将其形成区域的富含 dAl 的信号携带到开放的 AS。然而，在研究期间，温跃层水中的 dAl 富集主要局限于北部和西北部。在 AS 北部 Murray Ridge 的深水中观察到的相关溶解 Al 和 Fe 最大值表明 Al 和 Fe 从反应性粘土矿物（例如，伊利石）中释放出来，这些矿物大量存在于山脊上沉积的沉积物中。此外，在 AS 和 W-Eq.IO 的 Laxmi-Panikkar-Palitana 山脊系统 (~10.0 nM) 和 Carlsberg Ridge (~4.5 nM) 附近也分别观察到了升高的 dAl 水平。