Cross-Shelf Carbon Transport in the East China Sea and Its Future Trend Under Global Warming

The cross-shelf carbon transports across a section along the 100 m isobath from Taiwan to Cheju are estimated based on carbon concentration observations and ocean currents simulated by a regionally zoomed ocean-atmosphere coupled model. Results show that the net cross-shelf particulate organic carbon, dissolved organic carbon, and dissolved inorganic carbon transports are in the offshore direction at 1.81 +/- 0.22, 51.8 +/- 2.85, and 783 +/- 58.9 TgC yr-1, respectively, which are high in spring and summer and low in winter and fall following the seasonality of the offshore volume transport. The carbon is transported into the East China Sea (ECS) mainly by the Taiwan Warm Current and the Yellow Sea Warm Current, whereas they are carried out of the ECS mainly by the East China Sea Current extension and the recirculation north of Taiwan. Assuming steady biological activity, future net total organic carbon transports are projected to increase by 5%similar to 19% offshore at the end of the 21st century, with the maximum increase in winter, in a high greenhouse gas emission scenario of RCP8.5. The increased carbon transports are due to the increased offshore volume transport, transferring more carbon-rich coastal water away from the shelf in the warming future than at present. The results quantify cross-shelf carbon burial in the ECS in the background of global warming. Carbon transport due to water exchange between the continental shelf and the open ocean is one of the most important components of the world ocean carbon budgets. In this study, the cross-shelf carbon transport in the East China Sea (ECS) is estimated based on in situ carbon concentration observations and simulated ocean currents by an ocean-atmosphere coupled model. The use of the simulated currents is to avoid a bogus volume surplus in the estimates of the carbon transports. The offshore and the onshore volume transports, with significantly different carbon concentrations, are found to have a strong seasonal cycle and increase in the background of global warming, both of which are much larger than their difference, a.k.a. the net volume transport. As a result, the net cross-shelf carbon transports are in the offshore direction and are high in spring and summer and low in winter and fall. The organic carbon transports are projected to increase due to the ongoing global warming. These changes in the carbon burial need to be considered when assessing the impact of human activities and warming on the global carbon cycle. Our work would provide scientific evidence for increasing carbon sinks in the ECS in the warming future. Carbon transports across the ECS shelf were estimated based on carbon concentration observations and simulated currentsOffshore carbon transports are found induced by the ECSC from the inner shelf to the shelf breakThe organic carbon transports are projected to increase with the global warming at the end of the 21st century