Air-Sea Exchange Fluxes of CO2 in relation with Environmental Change


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My current research interests focus on marine biogeochemistry in relation with Environmental Change. The objective of research is the exchange across interfaces, such as the processes controlling air-water of CO2 and Hg. The recent study on gas-exchange flux dynamics of CO2 related to external forcing in the productive East China Sea (ECS), which is one of the largest East Asian marginal seas and the archetype of the continental shelf pump, was highlighted. From 8-years of our observations in the productive ECS shelf, we present the first dataset to show the complete seasonal cycle of CO2 flux, which gives an annual flux of 2.3±0.4 mol C m-2 y-1 as a net sink of atmospheric CO2. Further, we found evidence of strong control of river runoff on the CO2 uptake capacity of the ECS. Biological sequestration of CO2 takes place in the highly productive Changjiang river plume in warm seasons due to the riverine nutrient enrichment. Consequently, changes in the plume area due to changes in the Changjiang River Discharge strongly affect the CO2 uptake capacity. As the Discharge may decrease due to environmental changes through human perturbations (e.g., dam operation and water-transfer scheme), the Changjiang plume will probably also decrease, resulting in reduction in CO2 uptake capacity and even a shift from a CO2 sink to a source. This issue as the operation of the Three-Gorges Dam and its environmental impacts on the ECS CO2 uptake change is of great public concern and highly important.

Fig. 1 Conceptual diagram of the CO2 uptake dynamics in relation with the Discharge changes against with the strengths of Kuroshio and Taiwan Warm Current in the ECS shelf.


Fig. 2 Seasonal monthly pattern in CO2 flux obtained from field data and model results under conditions of the Discharge reduction by 10, 20, and 50% of the climatological mean during the study period of 2003-2010.