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- Title
Quantitative Assessment of Factors Contributing to Variations in Sea Surface pCO<sub>2</sub> in the Pacific Sector of the Arctic Ocean.
- Authors
Tozawa, Manami; Nomura, Daiki; Matsuura, Mirai; Hatta, Mariko; Fujiwara, Amane; Yasunaka, Sayaka; Murata, Akihiko
- Abstract
To quantitatively assess seasonal variations in the partial pressure of carbon dioxide (pCO2) in the Pacific sector of the Arctic Ocean (Canada Basin and Chukchi Sea) in 2021, water temperature, salinity, chlorophyll‐a, pCO2, dissolved inorganic carbon (DIC), total alkalinity (TA), and nutrients were measured. During summer 2021, surface water pCO2 in our study area (315 ± 41 μatm) was undersaturated with respect to the atmosphere (404 ± 4 μatm), and the ocean was a sink for atmospheric CO2 (−10.5 ± 11.0 mmol C m−2 day−1). Using DIC, TA, and nutrients in the temperature minimum layer, we estimated the under‐ice pCO2 in the water during the previous winter and calculated changes in pCO2 (δpCO2) due to temperature changes, freshwater inflow, biological activity, and other factors (gas exchange and advection) from winter to summer. In the Chukchi Sea, biological activity and temperature changes had significant impacts on pCO2, whereas in the Canada Basin, the influx of freshwater caused a significant decrease in pCO2. Our results suggested that different types of freshwaters had different effects on pCO2, with sea ice meltwater having a greater effect on reducing pCO2 than river water or snowmelt water. We therefore emphasize the importance of freshwater type and proportion, as well as freshwater supply, for prediction of future pCO2 changes. Plain Language Summary: Assessment of the factors that cause ocean CO2 to vary is important in the Arctic Ocean, which acts as an atmospheric CO2 sink that will change significantly because of global warming. Seawater and sea ice samples were collected in the Pacific sector of the Arctic Ocean to investigate the carbonate chemistry. The partial pressure of carbon dioxide (pCO2) was lower on the sea surface than in the atmosphere during summer, and the ocean absorbed atmospheric CO2. The decreases of pCO2 from winter to summer were driven primarily by biological activity in the Chukchi Sea (partially offset by temperature increases) and by freshwater additions in the Canada Basin. Sea ice meltwater, snow meltwater, and river water had different effects on pCO2, even though all of them diluted the carbonate concentrations of surface water, because of differences in the alkalinity and carbonate chemistry among these freshwater sources. Key Points: The Pacific sector of the Arctic Ocean absorbed atmospheric CO2 in summerIn the Chukchi Sea, biological activity and temperature changed pCO2, while in the Canada Basin, the freshwater caused a decrease in pCO2Sea ice meltwater had a greater effect on reducing pCO2 than river water or snow meltwater
- Subjects
CANADA Basin; ATMOSPHERIC carbon dioxide; OCEAN; PARTIAL pressure; LANGUAGE ability testing; WATER chemistry; SEA ice; CARBON dioxide
- Publication
Journal of Geophysical Research. Oceans, 2024, Vol 129, Issue 6, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2024JC021012