1. Riverine Influences and Seasonal Dynamics: Exploring Carbonate System Variations and Air‐Sea CO2 Fluxes in the Southern Yellow Sea and East China Sea.
- Author
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Li, Bing‐Han, Gong, Jiang‐Chen, Liu, Chun‐Ying, Hu, Jing‐Wen, and Yang, Gui‐Peng
- Subjects
SPRING ,VERTICAL mixing (Earth sciences) ,REGIONS of freshwater influence ,SEASONS ,TERRITORIAL waters ,CARBON cycle ,CARBONATES ,ATMOSPHERIC carbon dioxide - Abstract
In this work, the seasonal variations of the carbonate system and air‐sea CO2 fluxes were investigated by two cruises in the southern Yellow Sea (SYS) and the East China Sea (ECS), which were significantly influenced by the Changjiang riverine inputs across seasons. Biological‐mediated change of dissolved inorganic carbon (DIC) was first quantitated through a three end‐member mixing model from winter to spring. Our modeling results suggested that DIC addition through biological remineralization persisted in the SYS during winter and spring, while DIC removal was evident in the Changjiang River Plume and the offshore ECS triggered by river inputs in spring. Horizontal and vertical mixing together constituted the largest contribution to the interseasonal variability of partial pressure of CO2 (pCO2) in the SYS (−69.5%), the river plume (−59.3%), and the ECS offshore (−43.8%), followed by temperature effects in the plume area (29.4%), and biological processes in the ECS offshore (24.1%) and the SYS (−7.7%), with air‐sea CO2 exchange contributing the least in both three subregions. The SYS, the river plume, and the ECS offshore all acted as atmospheric CO2 sinks in both winter and spring. Furthermore, their ability to absorb atmospheric CO2 increased from winter to spring, as reflected in a ∼1.8‐fold increase in the overall spring air‐sea CO2 flux compared to winter estimation. Plain Language Summary: The carbonate system has played an essential role in regulating the ocean carbon cycle due to its buffer capacity for ocean acidification, especially in continental shelf seas. However, complex biological and physical processes present difficulties in assessing the seasonal dynamics of the carbonate system and following air‐sea CO2 fluxes. In this study, seasonal variations of the carbonate system were identified in the southern Yellow Sea (SYS) and the East China Sea (ECS). From winter to spring, biological DIC addition happened in the SYS, while DIC removal by biological production exceeded the addition by remineralization and caused most springtime DIC consumption in the river plume and the ECS offshore. We also quantified pCO2 variations from winter to spring, revealing the importance of physical mixing in controlling the ocean carbon cycle. Our study regions acted as atmospheric CO2 sinks in winter and spring, and their sink capacity was strengthened from winter to spring. Key Points: Dissolved inorganic carbon (DIC) addition occurred in the southern Yellow Sea (SYS) during winter and spring, while springtime DIC removal occurred in the river plume and the East China Sea (ECS) offshorePhysical mixing became the primary factor in regulating the interseasonal variation of pCO2The capacity of coastal waters in absorbing atmospheric CO2 was enhanced from winter to spring [ABSTRACT FROM AUTHOR]
- Published
- 2024
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