Contribution of Smoke Aerosols From Wildfires in Indo‐China Peninsula to the Western Pacific Ocean Carbon Sink.

Smoke aerosols from wildfires play a vital role in marine ecosystems and the ocean carbon cycle. This study analyzed a severe wildfires incident occurred in the Indo‐China Peninsula on 26 March 2019, and assessed its impact on ocean carbon sink. The satellite observations showed that the wildfires covered an area of about 56% of the entire peninsula, burning an area of 1.17 × 106 km2. Consequently, the wildfires discharged about 0.43 × 109 kg carbon. Moreover, a substantial amount of smoke released by severe wildfires was carried downstream by the wind and reached the western Pacific Ocean within 2 days. These smoke aerosols contribute to the ocean carbon sink through the mechanisms of the biological pump and their own carbon deposition. Model simulation results showed smoke aerosols contribute 6.44 × 104 kg black carbon to surface ocean by their own carbon deposition. Moreover, during the period of smoke aerosol's deposition, the flourishing growth of phytoplankton resulted in an increased carbon export of 0.25 ± 0.09 × 109 kg carbon (the biological pump mechanism), which represented approximately 57.97% ± 20.30% of the carbon emissions originating from the wildfire‐affected source region. Our research showed a positive impact of large wildfires on the ocean carbon sink, indicating the potential of smoke aerosols to alleviate the climate pressures resulting from carbon dioxide released by wildfires through improving the capacity of ocean carbon sink. Plain Language Summary: Wildfires emit substantial amounts of carbon dioxide into the atmosphere within a short timeframe. The ocean can mitigate the environmental impact of these wildfire events by fixing carbon. As one of the world's fire hotspot and the most significant burning area in the whole of Asia, it is necessary to understand the contribution of smoke aerosols emitted from the Indo‐China Peninsula to the Pacific Ocean carbon sink. We found that the source area of wildfires emitted 0.43 × 109 kg of carbon on 26 March 2019, and the smoke aerosols emitted by wildfires were carried by winds to the western Pacific Ocean within two days, and inputted 6.44 × 104 kg of black carbon. The increased ocean carbon export during the deposition of the smoke aerosol was 0.25 ± 0.09 × 109 kg, which is about half of the carbon emissions caused by wildfires. The results of this study suggest that smoke aerosols can contribute to the oceanic carbon sink, thereby alleviating the pressure on carbon emissions caused by wildfires. Key Points: A severe fire incident which account for 56% of the land area of the Indo‐China Peninsula has been researchedContribution of smoke aerosols to surface ocean carbon sink is primarily attributed by biological pump rather than carbon self‐depositionThe ocean assimilates around 57.97% ± 20.30% of the carbon emissions released by wildfires [ABSTRACT FROM AUTHOR]