High-accuracy ship-based observations were conducted at 80°E in the Indian Ocean. Salinity below the mixed layer in 2019 was observed to be lower than that in 1995. This decrease in salinity was mainly attributed to anomalous advection associated with one of the strongest positive Indian Ocean dipole (pIOD) events in 2019 through analysis of the gridded time series of the salinity distributions based on the Argo float array. Increases and decreases in nitrate and dissolved inorganic carbon (DIC) and dissolved oxygen (DO), respectively, were also detected on the isopycnal surfaces where decreases in salinity were observed, suggesting that the anomalous upwelling and westward advection associated with the pIOD in the eastern part of the equatorial region resulted in low-salinity, low-oxygen, and nutrient-rich waters in the central off-equatorial region of the Indian Ocean. However, downward isopycnal heaving, which was also associated with the pIOD, was too strong to have increased nitrate below the mixed layers, and thus might have suppressed biological activity. The heaving also affected the DIC and DO distributions, and the effect of interannual changes such as those associated with the Indian Ocean dipole is essential to estimating changes in anthropogenic carbon storage. This research represents a case study, based on only two occupations; therefore, an assessment utilizing more intensive observations and more realistic numerical simulations is necessary in the future.

在印度洋 80°E 进行了高精度船基观测。观察到 2019 年混合层以下的盐度低于 1995 年。盐度下降主要归因于与 2019 年最强的正印度洋偶极子 (pIOD) 事件之一相关的异常平流，通过对网格时间序列的分析基于 Argo 浮点数组的盐度分布。在盐度降低的等密度表面上也分别检测到硝酸盐和溶解无机碳（DIC）和溶解氧（DO）的增加和减少，这表明与东部pIOD相关的异常上升流和向西平流赤道部分地区低盐、低氧，印度洋中部非赤道地区营养丰富的水域。然而，也与 pIOD 相关的向下等密度起伏太强以至于无法在混合层下方增加硝酸盐，因此可能抑制了生物活性。起伏也影响了 DIC 和 DO 分布，而年际变化的影响，例如与印度洋偶极子相关的影响，对于估计人为碳储存的变化至关重要。这项研究代表了一个案例研究，仅基于两个职业；因此，未来有必要利用更深入的观察和更现实的数值模拟进行评估。太强以至于无法在混合层下方增加硝酸盐，因此可能会抑制生物活性。起伏也影响了 DIC 和 DO 分布，而年际变化的影响，例如与印度洋偶极子相关的影响，对于估计人为碳储存的变化至关重要。这项研究代表了一个案例研究，仅基于两个职业；因此，未来有必要利用更深入的观察和更现实的数值模拟进行评估。太强以至于无法在混合层下方增加硝酸盐，因此可能会抑制生物活性。起伏也影响了 DIC 和 DO 分布，而年际变化的影响，例如与印度洋偶极子相关的影响，对于估计人为碳储存的变化至关重要。这项研究代表了一个案例研究，仅基于两个职业；因此，未来有必要利用更深入的观察和更现实的数值模拟进行评估。仅基于两种职业；因此，未来有必要利用更深入的观察和更现实的数值模拟进行评估。仅基于两种职业；因此，未来有必要利用更深入的观察和更现实的数值模拟进行评估。