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Journal of Tropical Oceanography >

2016 , Vol. 35 >Issue 3: 55 - 64

DOI: https://doi.org/10.11978/2015035

Marine Chemistry

Distributions of partial pressure of carbon dioxide and sea-air CO2 flux in the western South China Sea in autumn*

  • XU Xin ,
  • YU Peisong ,
  • CAI Xiaoxia ,
  • PAN Jianming ,
  • HU Ji ,
  • ZHANG Haifeng
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  • Laboratory of Marine Ecosystem and Biogeochemistry, State Oceanic Administration; Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China

Received date: 2015-03-09

  Online published: 2016-05-27

Supported by

Global Change and Ocean-Atmosphere Interaction (GASI-03-01-02-02, GASI-03-01-03-02, GASI-03-01-06-05); National Natural Science Foundation of China (91128212)

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Abstract

Distribution of pCO2 in the surface water of the western South China Sea (SCS) was examined using data for autumn 2012. In this study, the control factors of surface pCO2 were investigated and sea-air CO2 flux in the study area was estimated. The results showed that sea surface pCO2 values of 37.8 to 57.1 Pa were observed in the western SCS. The sea surface pCO2 was always higher than that in the atmosphere, which indicated the western SCS acted as a source of the atmosphere CO2 in autumn. In the study area, sea surface pCO2 was mainly controlled by carbonate thermodynamics, and sea surface temperature (SST) was the predominant factor that controlled pCO2 distribution. However, sea surface pCO2 was also influenced by other factors in some areas. The transport of Mekong River diluted water led to low surface salinity water located in the Vietnamese eastern offshore region. Water mixing between Mekong River diluted water with high pCO2 and offshore water affected the regional surface pCO2 distribution directly. Furthermore, calcification process of coral reef organisms caused extremely high sea surface pCO2 to exist in the western Swallow Reef of the Nansha Islands. The CO2 outgassing rate of the western SCS in autumn was mainly influenced by sea surface wind speed, with average CO2 outgassing rate of 2.9 mmolC·m-2·d-1 in the northern continental shelf and northern basin and of 0.9 mmolC·m-2·d-1 in the central and southern basins. The effect of metabolism of coral reefs in regional areas should not be neglected in CO2 flux estimation.

Key words： the Western South China Sea; partial pressure of carbon dioxide; sea-air CO2 flux

Cite this article

XU Xin , YU Peisong , CAI Xiaoxia , PAN Jianming , HU Ji , ZHANG Haifeng . Distributions of partial pressure of carbon dioxide and sea-air CO2 flux in the western South China Sea in autumn*[J]. Journal of Tropical Oceanography, 2016 , 35(3) : 55 -64 . DOI: 10.11978/2015035

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