Seasonal and Yearly Controls of CO2 Fluxes in a Tropical Coastal Ocean

• Published in: Earth interactions 2023-01, Vol.27 (1)
• Main Authors: Swesi, Abdulghani, Yusup, Yusri, Ahmad, Mardiana Idayu, Almdhun, Haitem M., Jamshidi, Ehsan Jolous, Sigid, Muhammad Fikri, Ibrahim, Anis, Kayode, John Stephen
• Format: Article
• Language: English
• ISSN: 1087-3562; 1087-3562
• DOI: 10.1175/EI-D-22-0023.1

Carbon dioxide (CO 2 ) flux from Earth’s surface is a critical component of the global carbon budget, and the ocean surface is a significant CO 2 source and sink. The tropical coast absorbs CO 2 due to phytoplankton abundance and the all-year availability of photosynthetically active radiation. However, the role of the tropical coastal ocean in the global carbon budget is uncertain because of its underrepresentation in the literature. This study is the first to describe the variations of long-term CO 2 flux in the tropical coast on monthly and annual scales using the eddy covariance method and remote sensing data. The 5-yr average of the CO 2 flux is −0.089 ± 0.024 mmol m −2 day −1 , which indicates that it is a moderate carbon sink. The results show that the CO 2 flux varied seasonally: the fall transitional, southwest, spring transitional, and northeast monsoons partitioned the flux into three phases: increasing, stable, and decreasing. The rising and falling stages can be identified by the erratic behavior of the flux, whereas the stable phase’s fluxes were relatively constant. The environmental parameters that regulated CO 2 flux were chlorophyll a, sea surface temperatures, wind, and atmospheric stability, which modulated the CO 2 flux on the monthly time scale. Wavelet analysis corroborated the finding and revealed the role of photosynthetically active radiation (PAR) on CO 2 flux through El Niño–Southern Oscillation. On the monthly time scale, sea surface temperature only slightly affected the fluxes, unlike chlorophyll a, but temperature’s control on the flux became more apparent on the yearly time scale. These findings help us to understand the monthly and yearly controls of CO 2 flux and could contribute to developing models for predicting the flux on the tropical coast.