Air–Sea CO2 Exchange Over the Mediterranean Sea, the Red Sea and the Arabian Sea

Abstract

Anthropogenic greenhouse gas emissions are reshaping oceanic CO₂ uptake patterns. This study focuses on the crucial regions of the Arabian Sea, Red Sea, and Mediterranean Sea which are highly affected by human-caused climate change, aiming to unravel the complexities of air–sea CO₂ exchange dynamics. Understanding these processes is essential for predicting climate changes and assessing the health of marine ecosystems. In this context, a combination of observation-based data (Oc_v2020), and a multi-model ensemble of climate model simulations, were employed to explore the spatial and temporal variations in air–sea CO₂ flux (FCO₂) over these areas from 1982 to 2019. We implemented the Bayesian Model Averaging approach on the model outputs, resulting in a better representation of simulated CO₂ flux. Overall, climate models seem to underestimate the FCO₂ over the western Arabian Sea. We speculate that this model failure is attributed to the negative biased in vertical water velocity and the unrealistically representation of carbon release during coastal upwelling processes in the model. Our findings suggest that CO₂ source across the Red Sea, the Arabian Sea, and the central region of the Mediterranean Sea has been reduced with a trend of − 0.494 ± 0.009, − 1.350 ± 0.001, and − 0.329 ± 0.074 gCm⁻² year⁻¹ decade⁻¹, respectively. In contrast, the CO₂ sink across the Western Mediterranean has been enhanced with a trend of − 0.793 ± 0.086 gCm⁻² year⁻¹ decade⁻¹. In general, change in the water temperature was recognized as the major contributor to the sea surface partial pressure of CO₂ (pCO₂). The exception was found in the Arabian Sea, where non-thermal effects play the major role. Our results show that the CO₂ flux variation is accompanied by regional changes in the sea surface pCO₂. Across the North Arabian Sea, FCO₂ is also correlated with the surface wind variability, which is likely due to the changes in wind-driven upwelling. In conclusion, our study advances the understanding of regional air–sea CO₂ exchange dynamics, emphasizing the need for improved model representation in areas with intense seasonal upwelling. The prominent changes in the Arabian Sea, underscore the immediate necessity for science-based management in this region to mitigate the impacts of human-induced global warming.