This paper examines the seasonal variability of surface ocean pCO₂ and pH in the northern Indian Ocean. It aims to identify their controlling factors using a high-resolution, regional ocean-ecosystem model simulation and available surface ocean carbon observations. The seasonal variability of pCO₂ and pH of the northern Indian Ocean is attributed to the changes in surface temperature (T), dissolved inorganic carbon (DIC), total alkalinity (ALK), and salinity (S). The western Arabian Sea has an enormous seasonal variance of pCO₂ due to coastal upwelling dynamics. In contrast, the seasonal variance of pCO₂ in the Bay of Bengal is governed by the upper ocean mixed layer dynamics, albeit with smaller amplitudes. The contribution of T (DIC) in the seasonal variance of pCO₂ and pH at the western Arabian Sea is ±90 (∓100) μatm and ±0.18 (∓0.20) pH units, respectively. The contribution of ALK and S is complementary to each other in inducing seasonal variances of pCO₂ and pH in the southeastern Arabian Sea with a magnitude of ±5∼10 μatm and ±0.02 pH units, respectively. In the northern Bay of Bengal, salinity plays a significant role in controlling seasonal variability of pCO₂ and pH with amplitudes of roughly ±20 µatm and ±0.18 pH units, respectively, along the pathways of freshwater spreading. The maxima of seasonal amplitudes of pCO₂ and pH occur during April-May and August-September for both basins. This study highlights the hotspots of pCO₂ and pH in the northern Indian Ocean, where observational efforts to monitor pCO₂ and pH become an essential requirement.

本文研究了北印度洋表层海洋 pCO ₂ 和 pH 值的季节性变化。它旨在使用高分辨率的区域海洋生态系统模型模拟和可用的表面海洋碳观测来确定其控制因素。北印度洋pCO ₂和 pH 值的季节性变化归因于地表温度 (T)、溶解无机碳 (DIC)、总碱度 (ALK) 和盐度 (S) 的变化。由于沿海上升流动力学，阿拉伯海西部的 pCO ₂具有巨大的季节性变化。相比之下，pCO ₂的季节性变化孟加拉湾的海洋受上层海洋混合层动力学控制，尽管振幅较小。T (DIC) 对阿拉伯海西部pCO ₂和 pH的季节性变化的贡献分别为 ±90 (∓100) μatm 和 ±0.18 (∓0.20) pH 单位。ALK 和 S 在引起阿拉伯海东南部pCO ₂和 pH 的季节性变化方面相互补充，幅度分别为 ±5∼10 μatm 和 ±0.02 pH 单位。在孟加拉湾北部，盐度在控制 pCO ₂和 pH 的季节性变化方面起着重要作用，其幅度分别约为 ±20 µatm 和 ±0.18 pH 单位，沿着淡水扩散路径。pCO ₂季节性振幅的最大值和 pH 值发生在 4-5 月和 8-9 月两个盆地。这项研究突出了北印度洋pCO ₂和 pH 值的热点，在那里监测 pCO ₂和 pH 值的观测工作 成为一项基本要求。