The upwelling phenomena revealed by the historic hydrologic survey data in the northern South China Sea and their formation mechanisms
It prevails southwesterly monsoon in summer in the northern South China Sea.Consequently,the season-al coastal upwellings are frequently driven up in summer off the southeastern coast of the Hainan Island,the east-ern coast of the Leizhou Peninsula and the eastern coast of Guangdong Province,and these upwellings have attrac-ted common research attention.The present paper revisits the historic hydrologic survey data in the northern South China Sea.It is found that,besides the coastal upwellings frequently reaching the sea surface in the above-men-tioned zones,there are more subsurface upwelling patterns in the northern South China Sea:namely,(1)the subsur-face upwelling throughout the eastern coastal zones of Hainan Province and all the western and eastern coastal zones of Guangdong Province under strong overlying southwesterly monsoon;(2)the subsurface one over the wide continental shelf off the western coast of Guangdong Province;(3)the subsurface one driven by the diluted Pearl River runoff off the river mouth;and(4)the bottom continental water invasion into the bays of eastern Guangdong Province and the cyclonic eddies in the bays.These four upwelling patterns have not been reported in the existing research papers,or little attention has been paid to them.Besides the Ekman's transport due to strong summer south-westerly monsoon and Ekman's pumping due to overlying wind stress curl,the bottom Ekman's effect due to the basin-scale South China Sea circulation is possibly the non-negligible driving mechanism for the subsurface up-welling throughout all the coastal zones.In the light of the simultaneous atmospheric circulation over the northern South China Sea,Ekman's pumping due to positive wind stress curl seems to be the major driving force for the sub-surface upwelling over the continental shelf off western Guangdong coast.The positive wind stress curl as well as the diluted Pearl River runoff drives a cyclonic circulation off western Guangdong coast.The seawater divengence in the cyclonic circulation is favorable to the formation and maintenance of the subsurface upwelling.The vertical circulations driven by southwesterly monsoon and horizontal cyclonic ones in the coastal bays of eastern Guang-dong Province are the major driving forces for the bottom continental water intruding into the bays.In the Daya Bay,the thermal plume due to the unclear power plants is favorable to strengthen the horizontal cyclonic circula-tions.The western and eastern capes of the Honghai Bay are favorable to the formation of horizontal cyclonic circu-lations in the bay.So we need attach more importance to the other driving mechanisms of the upwelling but to sur-face Ekman's effect in the northern South China Sea.
the northern South China Seaupwellingthe diluted Pearl River runoffcurl of wind stressvertical circula-tion
万方数据
维普
