Investigation the impact of methane leakage on the marine carbon sink

Methane (CH4) leaks have traditionally been thought to dramatically affect the marine carbon sinks, as CH4 was a greenhouse gas that contributes about 30 times more than CO2. However, research vessels in the Arctic have found that in areas with CH4 leakage on the seafloor, the levels of CO2 in the atmosphere are low. In order to prove this point and quantify the impact of methane leakage on the marine carbon sinks, a multiple physical fields model was built, which considered the roles of nutrients carried by CH4 leakage, photosynthesis by algae, the changes of seawater flow field, and the solute transport processes of carbon component. Moreover, we predicted whether this phenomenon still exists in different regions. The results showed that methane leakage have a positive impact on marine carbon sinks, mainly manifested in two aspects: methane bubble plumes bring low-temperature and low salinity seawater from the bottom to the surface, contribute to the dissolution of CO2; the CH4 bubbles transport nutrient-rich substances from the seafloor to the sea surface promote the photosynthesis of algae. The analysis of the impact of methane leakage parameters indicates that the increase in leakage rate and leakage temperature both contribute to the increase in total accumulated negative carbon content. In the study of leakage rates, it was found that the continuous increase in nutrient concentration will no longer affect photosynthesis after reaching a certain threshold. The dominant effect was the positive feedback of CO2 dissolution caused by the continuous decrease in seawater temperature and salinity. The increase in leakage temperature can offset the influence of low-temperature seawater in the upwelling flow, thereby enhancing photosynthesis but increasing Henry's constant (decrease in CO2 dissolution rate). At higher leakage rates, changes in leakage temperature have a more significant impact on marine carbon sink potential. It is worth noting that the positive impact of methane leakage on the marine carbon sink still exists but the degree of enhancement may be diminished in tropical regions with higher temperatures.