The Impact of Anomalous Biomass Burning on Phytoplankton and Surface Ocean Carbon Pool in the Indo-China Peninsula

Abstract

The ocean carbon sink plays a pivotal role in absorbing carbon dioxide and combating climate change. By utilizing satellite data, this study identified an exceptionally severe biomass burning event in the Indo-China Peninsula on 31 March 2020. This incident engulfed most of the island, with a total of 3,550 fires, representing the highest number of fire points from 2015 to 2023. Furthermore, this abnormal burning released 5.71 × 10⁹ kg of carbon dioxide in the dense fire area, accompanied by smoke aerosols that were rich in nutrients and carbon. These smoke aerosols were transported to the western Pacific Ocean by the subtropical high boundary stream. Upon deposition into the ocean, the smoke aerosols triggered a maximum increase of 314% in chlorophyll a concentration, as compared to the average for April 2020. This significant stimulation of phytoplankton growth indirectly contributed to the expansion of the surface ocean carbon pool. During their deposition, carbon export through the biological pump mechanism was 3.13 ± 1.27 × 10⁸ kg. Although anomalous wildfires emitted more smoke aerosols, there was no significant increase in ocean carbon export. Ultimately, the response of the surface ocean carbon pool to the influence of smoke aerosols partially offset about 20.06 ± 7.51% of the carbon emissions. Additionally, smoke aerosols directly increased the surface ocean carbon pool by 2.64 × 10⁷ kg through their own carbon deposition mechanism. Our study demonstrated that the ocean's capacity for carbon uptake is constrained. The carbon dioxide emissions from anomalous biomass burning events significantly surpass those that the ocean can effectively assimilate.