Enhanced Carbon Sink Through Medium‐Level Tropical Cyclones in the Offshore East China Sea

Abstract

Remote‐sensing data show that both the carbon source and carbon sink are likely to occur during strong tropical cyclone (TC) processes, indicating changeable mechanisms in air‐sea CO ₂ flux (FCO ₂ ) during an individual TC process. However, the overall TC‐induced FCO ₂ , as well as the quantification of its mechanisms throughout the entire TC process, remains difficult to assess. This study focuses on the total TC‐induced FCO ₂ response in the offshore East China Sea, a representative shallow‐shelf system where seawater responds rapidly to wind stress and TC disturbances. Based on a well‐validated carbon flux model, 34 historical TCs during the past 17‐year revealed an average carbon sink (−2.51 mmol m ⁻²  d ⁻¹ ) that was nearly twice as strong as the background sink (−1.31 mmol m ⁻²  d ⁻¹ ). The medium‐level TCs in late summer, which not only maintained low dissolved inorganic carbon in the surface layer to generate negative FCO ₂ but also provided enough wind turbulence to enhance the FCO ₂ magnitude, mainly contributed to the strong sink effects. Furthermore, the background ocean stratification indirectly modulates the FCO ₂ response to TCs, with a deeper and stronger cline being more conducive to TC‐induced carbon uptake.