Different Types of Freshwaters Have Different Impacts on Sea Surface pCO2 in the Arctic Ocean

The Arctic Ocean uptake carbon dioxide (CO₂) from the atmosphere strongly because of its low partial pressure of carbon dioxide (pCO₂). Sea surface pCO₂ varies due to temperature, freshwater, and biological activity. In addition, the Arctic Ocean is strongly affected by global warming. To predict the future impact of environmental changes on CO₂ exchange, it is important to quantitatively assess the factors contributing to variations in sea surface pCO₂. By investigating the carbonate chemistry in the sea ice meltwater to assess the freshwater effect, we found that low salinity sea ice has higher pCO₂ despite of lower dissolved inorganic carbon (DIC) and total alkalinity (TA). It means that lower salinity meltwater, such as snow meltwater and multi-year ice meltwater, has smaller effect on reducing pCO₂ than meltwater from younger sea ice. Therefore, changes in the inflow of each freshwater type must be estimated, and their impact on pCO₂ must be assessed.

Reference: Tozawa, M., Nomura, D., Matsuura, M., et al. (2024). Quantitative assessment of factors contributing to variations in sea surface pCO₂ in the pacific sector of the Arctic Ocean. J. Geophys. Res.: Oceans, 129, e2024JC021012. https://doi.org/10.1029/2024JC021012