476 / 2024-09-17 21:31:53

The 2023 summer drought and high temperature turn the East China Sea off the Changjiang estuary from a CO2 sink to a CO2 source

East China Sea, Changjiang estuary, summer drought, pCO2, air-sea CO2 flux, CO2 source, discharge

This study reports the surface water partial pressure of CO₂ (pCO₂) and air-sea CO₂ fluxes in the East China Sea shelf off the Changjiang estuary in August 2023. Surface water pCO₂ ranged from 110-910 matm with an average value of 427.2±154.0 matm. Air-sea CO₂ fluxes in the surveyed area ranged from -20.6 mmol m^-2 d^-1 to 35.9 mmol m^-2 d^-1 and averaged to 3.0±8.9 mmol m^-2 d^-1 (moderate source), which was contrary to the general cases of CO₂ sink in this system in summer. Changjiang discharge has vital impact on the surface water pCO₂. The decreased Changjiang discharge in August 2023 increased the surface water pCO₂ substantially, and the high sea surface temperature further elevated the surface water pCO₂. The combined effect of drought and high temperature in August 2023 turned the study area from a CO₂ sink to a CO₂ source. Under the context of global change, climate events such as floods, droughts, heatwaves occur more frequently, which add more complexity to the CO₂ sink/source evaluation in large river dominated marginal seas, which needs more studies.