Carbon Dioxide Variations in and around the South China Sea
| Autor: | Wei-Ping Hou, 侯偉萍 |
|---|---|
| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 The purpose of this study was to discuss the CO2 variation in and around the South China Sea (SCS), the largest marginal sea in the world. The SCS and Sulu Sea (SS) in November and December respectively, were a small CO2 source to the atmosphere. The West Philippine Sea (WPS) was a large CO2 source to the atmosphere in September. Due to strong upwelling and mixing in the SCS, the excess CO2 penetrated only to approximately 1000m compared to 1200m in the WPS. Because the SCS subsurface water flows to the SS through the 420 m-deep Mindoro Strait, the excess CO2 in the SS was found throughout the entire water column. According to NOAA, 2002 was a weak-to-moderate strength ENSO year and the second warmest since 1986. The Taiwan Strait is the sole passage which connects the East and South China Seas, but the CO2 variation in the Taiwan Strait is unclear during the ENSO year. We heady discuss the relation between the ENSO and CO2 variation in the Taiwan Strait. During the ENSO year, the Penghu Channel mixed in more Kuroshio water but the upwelling strength weakened. During an ENSO event, the southwest monsoon and surface circulation are weaker than normal, hence there is less SCS water flowing to the Penghu Channel. Primary productivity in the non-ENSO year (2001) was high so the fCO2 was low in the upwelling area in the Penghu Channel. The Δ fCO2(sea-air) was about 15µatm and 20µatm in the non-ENSO year and the ENSO year, respectively. The southern Taiwan Strait was a source of CO2 in summer. The hydrology in the northern Taiwan Strait in summer was comprised mainly of two different water masses. A salinity front was found at between 25.67oN, 121.24oE and 25.87oN, 120.95oE in the non-ENSO year and at between 25.67oN, 121.24oE and 25.77oN, 121.08oE in the ENSO year. There was coastal upwelling in the western Taiwan Strait in the ENSO year. In the ENSO year, the southward flowing China Coastal Current in winter (January to March) was weaker than normal, which led to a higher percentage of northward flowing water mass in summer. As a result, the summer time salinity in the surface layer became higher so the vertical density gradient became lower than a normal year. East of the front was the Kuroshio and west of the front was the water mass that flew through the Taiwan Strait. The Kuroshio is high in temperature and salinity so the fCO2 to the east of the front was higher than found west of the front in the non-ENSO year. In the ENSO year, owing to the coastal upwelling, the fCO2 near the Chinese coast was higher than east of the front. The northern Taiwan Strait had a Δ fCO2(sea-air) of about 21µatm and 16µatm in the non-ENSO and the ENSO years, respectively, and it was still a source of CO2 in summer. |
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