[Changes of oceanic dissolved inorganic carbon and the regulation of ocean carbon sink]

Dissolved inorganic carbon (DIC) constitutes a major component of carbon reservoir in ocean and plays a pivotal role in regulating global carbon cycle. However, the distribution of DIC in global ocean exhibits pronounced spatial and temporal variations. Vertically, the concentration of DIC increases gradually from the surface to the depth; horizontally, surface DIC exhibits a pattern characterized by lower concentrations in low-latitude regions and higher concentrations in high-latitude oceans, with upwelling regions presenting elevated concentrations. Temporally, DIC exhibits significant seasonal, interannual, and decadal variations. Since the Industrial Revolution, the global concentration of DIC has risen at a rate of 1.5±0.3 μmol·kg^-1·a^-1, resulting in a net annual increase of 2.9±0.4 Pg C, which has altered the marine carbonate system and biological communities. Currently, due to the reliance on direct ocean surveys for DIC data, there is limited temporal and spatial coverage. DIC gridded datasets based on field observations and machine-learning algorithms can be used for studying the global-scale temporal and spatial variations of DIC and ocean carbon sinks. Under the background of global change, regional DIC trends are increasingly complex and require further investigations. We propose to enhance the ocean carbon sink by regulating DIC, which would hold significant scientific importance and potential applications.