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- Title
Spatiotemporal Variability of Aragonite Saturation State in the Northern East China Sea.
- Authors
Choi, Yujeong; Kim, Tae‐Hoon; Kim, Dongseon; Kang, Dong‐Jin
- Abstract
In order to evaluate the spatiotemporal distribution of the carbonate system in the northern East China Sea (ECS), we first measured the seasonal dissolved inorganic carbon (DIC) and total alkalinity (TA), from which the aragonite saturation state (Ωarag) was calculated for the years 2015–2017. The DIC, TA, and Ωarag were 1,680.9–2,211.4 μmol kg−1, 2,145.1–2,312.8 μmol kg−1, and 1.2–6.0, respectively. The spatiotemporal variability of Ωarag in the northern ECS was mainly controlled by seasonal water mass, such as Yellow Sea Surface Water, Changjiang Dilute Water, and Yellow Sea Bottom Water (YSBW). The lowest Ωarag (∼1.4) in bottom layer was observed in high primary production areas caused by the extension of the Changjiang River plume with the higher Ωarag (up to 6) and was closely linked to the YSBW with low Ωarag expanded southward from Yellow Sea near bottom. Although this area was not a hypoxia zone unlike western shelf region (Chinese region) of the northern ECS, YSBW near bottom could enhance the suppression of bottom aragonite without hypoxia. In eastern region of northern ECS, higher production at surface, YSBW with lower Ωarag extension, and longer respiration product accumulations near bottom tend to lower Ωarag, as compared with western region where the summer hypoxia led to lower Ωarag. Therefore, this result indicates that the eastern region of the northern ECS is also susceptible to ocean acidification, along with the summer hypoxic zone of the western region. Plain Language Summary: Excess carbon dioxide from fossil fuel burning enters the ocean and reacts with seawater decreasing ocean pH, and lowering carbonate ion concentrations. These chemical reactions are known as ocean acidification (OA). Aragonite saturation state (Ωarag) is generally used to trace OA because it measures carbonate ion concentration. A decrease in Ωarag affects marine calcifying organisms and marine ecosystem. In previous studies on OA in East China Sea (ECS), most data were confined to the western shelf region (Chinese region), and this has limited our knowledge about the state of OA for the entire ECS. This study is the first to explore spatiotemporal variability of Ωarag in the northern ECS (Korean region). We found that the spatiotemporal variability of Ωarag in the northern ECS was mainly controlled by seasonal water mass, such as Yellow Sea Surface Water, Changjiang Dilution Water, and Yellow Sea Bottom Water (YSBW). The lowest Ωarag (∼1.4) at the bottom layer was found in areas of surficial high primary production (Ωarag = 6.0), where the Changjiang River plume with nutrient‐rich water discharged and the YSBW with lower Ωarag expanded southward from Yellow Sea near bottom. This value was almost the same as that in areas of hypoxia in Chinese region. Compared with Chinese region, higher production at surface, YSBW with lower Ωarag extension, and long‐term respiration product accumulations near bottom tend to lower Ωarag. This result shows that the Korean region of ECS also could be also vulnerable to OA. Key Points: Dissolved inorganic carbon concentration was main driver of the seasonal variability of aragonite saturation state (Ωarag) in the northern East China Sea (ECS)Spatial variability of Ωarag was mainly controlled by seasonal water massThe northern ECS could be vulnerable to acidification due to high production, Yellow Sea Bottom Water expansion with low Ωarag, and long‐term remineralization
- Subjects
EAST China Sea; YELLOW Sea; SPATIOTEMPORAL processes; ARAGONITE; OCEAN acidification
- Publication
Journal of Geophysical Research. Oceans, 2022, Vol 127, Issue 1, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2021JC017593