Analysis on characteristics of CO₂ fluxes across the air-sea interface of the Yangtze Estuary and adjacent sea in late winter 2016

Based on the survey at the Yangtze Estuary and adjacent sea in March 2016, regional distributions of the surface water partial pressure of CO₂ and relevant parameters were analyzed, air-sea CO₂ fluxes were estimated and physical processes of CO₂ source/sink distribution were discussed.Results showed that the surface pCO₂ in survey area ranged from 321~575 μatm, generally exhibiting high values at the inner shelf, whereas low values off the shore.Until the end of winter, the distribution of surface pCO₂ had been dominated by the mixing between the estuarine water (low temperature, low salinity, high pCO₂) and the shelf water in the East China sea(high temperature, high salinity, low pCO₂), while vertical mixing had little effect on it.The Yangtze Estuary and adjacent sea also served as a weak sink of atmospheric CO₂, with a -4.43±7.41 mmol/m²/d average air-sea CO₂ flux.In the sight of regional carbon sink intensity, its level in the Changjiang Diluted Water was nearly in balance with that in the atmosphere.The Yellow Sea-East China Sea Mixing Water and Taiwan Warm Current Water were moderate/strong sink of the atmospheric CO₂, becoming a major contributor to the ocean absorbed CO₂ during winter.