Estimation of partial pressure of CO2 in seawater/ Air-sea CO2 flux - Air-Sea CO2 Flux

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Research Background

Since the onset of the industrial revolution, anthropogenic activities, particularly the combustion of fossil fuels, have led to a significant rise in atmospheric carbon dioxide (CO₂) levels. This increase in CO₂concentration has resulted in global warming, which poses substantial threats to the Earth's ecosystems, human habitats, and sustainable socio-economic development. Given that the ocean covers approximately 71% of the planet's surface area, it serves as a vital reservoir for atmospheric CO₂ and plays a crucial role in regulating global climate patterns. Understanding the exchange of CO₂ at the air-sea interface is fundamental for assessing the ocean's contribution to global changes. Accurate quantification of the air-sea CO₂ flux and a comprehensive understanding of its spatiotemporal variations are pivotal tasks in the study of the global carbon cycle and climate change. However, uncertainties persist in carbon cycle research, both in terrestrial and oceanic domains.

The objective of this research is to investigate the response of the ocean to the rising average atmospheric CO₂ concentration and examine the long-term changes in seawater partial pressure of carbon dioxide (pCO₂) and the corresponding sea-air CO₂ flux. This investigation will be carried out through large-scale simultaneous observations and the utilization of remote sensing data characterized by high temporal and spatial resolutions.

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Figures

Fig2 Climatological Monthly Average Results of Sea-to-Air CO2 Flux in the Coral Sea based on the MeSAA Algorithm for the period 2006-2018
Fig1: Climatological Monthly Average Results of Sea Surface CO2 Partial Pressure in the Coral Sea based on the MeSAA Algorithm for the period 2006-2018

Scientific Progress

The air-sea carbon dioxide (CO₂) fluxes in the Coral Sea are measured in mol m^-2 yr^-1 with the spatial resolution of 9 km × 9 km, covering the Coral Sea from January 2006 to December 2018. Validation of in situ measurements of the partial pressure of seawater CO₂ (pCO₂) showed a root-mean-square error of 9.88 μatm in the Coral Sea basin and 11.28 μatm in the coastal zone.

This dataset used atmospheric pressure data from the ERA-5, atmosphere CO₂ concentration data from CarbonTracker2019B, sea surface chlorophyll concentration data from the CCI, sea surface salinity data from the CMEMS, sea surface temperature data from the OISST, and sea surface wind velocity data from the CCMP. Using the MeSAA algorithm (which step-by-step resolves the effects of thermodynamic processes, biological processes, and atmospheric forcing on sea surface pCO₂, and establishes a semi-analytical inversion model of sea surface pCO₂ and the influencing factors in the ocean), a monthly coral sea surface pCO₂ product was produced for the period of 2006-2018. Then, combined with other environmental data, such as wind speed and atmospheric CO₂ concentration, we estimated the air-sea CO₂ flux products. Compared with similar global products, it contains all available regional information with no limitation to the provision of spatially consistent air-sea CO₂ sinks. Therefore, as the regional product has a higher spatial resolution and contains more details, such as regional specific information, it can be used for regional studies. This work provides a solid foundation for further research on ocean carbon sinks and their impacts by climate change.

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References

Zhang, Siqi, Yan Bai, Xianqiang He, Shujie Yu, Zigeng Song, Fang Gong, Qiankun Zhu, and Delu Pan. 2023. “The Carbon Sink of the Coral Sea, the World’s Second Largest Marginal Sea, Weakened during 2006–2018.” Science of The Total Environment 872 : 162219. https://doi.org/10.1016/j.scitotenv.2023.162219.

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Research Background

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Scientific Progress

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