Spatial variability in boundaries and thickness of oxygen minimum zone (OMZ) is derived based on measured dissolved oxygen data obtained from sensors on board biogeochemical (BGC) Argo floats between 2013 and 2019 in the Bay of Bengal (BoB). Upper and lower boundaries of the OMZ varied from 60 to 200 m and 100 to 800 m respectively with the thickness of 80–650 m in the BoB. Relatively thicker OMZ is noticed in the northern than southern BoB associated with stratification. The oxygen concentrations in the OMZ in the NW was low (<1.5 μM) than NE BoB (2.5 μM) indicating that thick and intense OMZ occurs in the NW region associating with stratification and high primary production. Significant decrease in particle-back-scatter signal was observed toward offshore from shelf indicating organic matter from the shelf sediments may be supporting bacterial carbon demand in the OMZ. The particle backscatter signal peaked in the OMZ region with a higher signal in the north than southern BoB and it is consistent with the low oxygen concentration in the former indicating that organic matter from shelf sediments may be supporting carbon needs in the OMZ. In addition to this, the occurrence of eddies significantly controls the intensity of the OMZ in the BoB through mixing at the upper boundary of OMZ. Therefore, this study suggests that spatial variations in intensity of OMZ in the BoB are governed by stratification, primary and export productions, organic matter decomposition, and eddy-driven mixing.

中文翻译：

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造成孟加拉湾最低氧区强度和厚度空间变异的潜在机制

2013 年至 2019 年间在孟加拉湾 (BoB) 的生物地球化学 (BGC) Argo 浮标上的传感器获得的测量溶解氧数据，推导出最低氧区 (OMZ) 边界和厚度的空间变异性。OMZ 的上下边界分别为 60～200 m 和 100～800 m，BoB 厚度为 80～650 m。在与分层相关的 BoB 北部，观察到相对较厚的 OMZ。NW OMZ 中的氧浓度比 NE BoB (2.5 μM) 低（<1.5 μM），表明 NW 区域发生厚而强烈的 OMZ，与分层和高初级生产相关。从陆架向近海观察到的粒子背散射信号显着减少，表明来自陆架沉积物的有机物质可能支持 OMZ 中的细菌碳需求。粒子背向散射信号在 OMZ 区域达到峰值，北部信号高于 BoB 南部，这与前者的低氧浓度一致，表明来自陆架沉积物的有机物质可能支持 OMZ 的碳需求。除此之外，涡流的出现通过在 OMZ 上边界的混合显着控制了 BoB 中 OMZ 的强度。因此，本研究表明 BoB 中 OMZ 强度的空间变化受分层、初级和出口生产、有机物质分解和涡驱动混合控制。粒子背向散射信号在 OMZ 区域达到峰值，北部信号高于 BoB 南部，这与前者的低氧浓度一致，表明来自陆架沉积物的有机物质可能支持 OMZ 的碳需求。除此之外，涡流的出现通过在 OMZ 上边界的混合显着控制了 BoB 中 OMZ 的强度。因此，本研究表明 BoB 中 OMZ 强度的空间变化受分层、初级和出口生产、有机物质分解和涡驱动混合控制。粒子背向散射信号在 OMZ 区域达到峰值，北部信号高于 BoB 南部，这与前者的低氧浓度一致，表明来自陆架沉积物的有机物质可能支持 OMZ 的碳需求。除此之外，涡流的出现通过在 OMZ 上边界的混合显着控制了 BoB 中 OMZ 的强度。因此，这项研究表明，BoB 中 OMZ 强度的空间变化受分层、初级和出口生产、有机物质分解和涡驱动混合控制。