Abstract

Shifts in surface ocean pCO₂ and pH are important controls governing global climate. Based on the linear relationship of observed surface pH and pCO₂ with sea surface temperature (SST), sea surface salinity (SSS) and Chlorophyll-a (Chl-a) multiple linear regression equations were developed. Based on remote sensing SST, Chl-a and model-derived SSS, pH and pCO₂ data were derived from 1998 to 2015. Overall warming of BoB is noticed at the rate of 0.004° to 0.03 °C/y whereas cooling is found in the northwestern BoB during winter and spring seasons associated with an increase in atmospheric dust. Decrease in SSS is noticed during all seasons due to melting of Himalayan ice cover associated with increase in fresh water flux due to increase in atmospheric temperature. Increase in pH is observed in the eastern and southern Bay during all seasons associating with warming and decrease in salinity. In contrast, decrease in pH (−0.001 y⁻¹) and pCO₂ increase (+0.1 to +0.7 µatm y⁻¹) is noticed in the western and head Bay during winter and spring seasons due to deposition of atmospheric pollutants. This study suggests that increase in freshwater input due to melting of Himalayan ice cover and deposition of atmospheric pollutants are dominant controlling factors on surface ocean pH and pCO₂ in the BoB between 1998 and 2015 and this region is acting as a stronger sink for the atmospheric CO₂ in the present than that in the past two decades. The global coastal regions are significantly influenced by river discharge and atmospheric deposition of pollutants and they are not part of the global models leading to ill-reproduction of seasonal variability in pH and pCO₂. Inclusion of these processes may improve prediction of pH and pCO₂ in the regions heavily influenced by discharge/deposition from land and atmosphere.

摘要

表层海洋 pCO ₂和 pH 值的变化是控制全球气候的重要控制因素。基于观测到的海面 pH 值和 pCO ₂与海面温度 (SST)的线性关系，开发了海面盐度 (SSS) 和叶绿素-a (Chl-a) 多元线性回归方程。基于遥感 SST、Chl-a 和模型衍生的 SSS、pH 和 pCO ₂数据来自 1998 年至 2015 年。 注意到 BoB 整体变暖的速率为 0.004° 至 0.03 °C/y，而在与大气灰尘增加相关的冬季和春季，BoB 西北部发现变冷。由于喜马拉雅山冰盖融化以及大气温度升高导致淡水通量增加，所有季节都注意到 SSS 下降。在与变暖和盐度降低相关的所有季节，在海湾东部和南部观察到 pH 值的增加。相反，pH 值降低 (-0.001 y ^-1 ) 和 pCO ₂增加 (+0.1 to +0.7 µatm y ^-1) 在冬季和春季，由于大气污染物的沉积，在西部和海角湾被注意到。这项研究表明，1998 年至 2015 年间，由于喜马拉雅冰盖融化和大气污染物沉积而导致的淡水输入增加是 BoB 中表层海洋 pH 值和 pCO _{2 的}主要控制因素，该地区正在充当更强大的大气汇。现在的CO ₂比过去二十年多。全球沿海地区受到河流排放和污染物大气沉积的显着影响，并且它们不是导致 pH 和 pCO ₂季节性变化的不良再现的全球模型的一部分。包含这些过程可能会改善对 pH 和 pCO 的预测₂在受陆地和大气排放/沉积影响严重的地区。