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LI Li,GAN Zijun. 2014. Ventilation of the Sulu Sea retrieved from historical data. Acta Oceanologica Sinica, 33(9):1-11
Ventilation of the Sulu Sea retrieved from historical data
Received:April 08, 2014  Revised:May 28, 2014
Key words:Sulu Sea  ventilation  overflow  interbasin exchange
中文关键词:  苏禄海  通风  海水更新过程  溢流  盆间交换
基金项目:The Chinese Ministry of Science and Technology through the National Basic Research Program under contract No. 2009CB421205.
Author NameAffiliationE-mail
LI Li Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China lili@tiosoa.cn 
GAN Zijun State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanoglogy, Chinese Academy of Sciences, Guangzhou 510301, China  
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      Based on historical observations, ventilation of the Sulu Sea (SS) is investigated and, its interbasin exchange is also partly discussed. The results suggest that near the surface the water renewal process not only occurs through the Mindoro Strait (MS) and the Sibutu Passage, but also depends on the inflows through the Surigao Strait and the Bohol Sea from the Pacific and through the Balabac Strait from the South China Sea (SCS). Both inflows are likely persistent year round and their transports might not be negligible. Below the surface, the core layer of the Subtropical Lower Water (SLW) lies at about 200 m, which enters the SS through the Mindoro Strait not hampered by topography. Moreover, there is no indication of SLW inflow through the Sibutu Passage even though the channel is deep enough to allow its passage. The most significant ventilation process of the SS takes place in depths from 200 m to about 1 200 m where intermediate convection driven by quasi-steady inflows through the Mindoro and Panay straits (MS-PS) dominates. Since the invaded water is drawn from the upper part of the North Pacific Intermediate Water (NPIW) of the SCS, it is normally not dense enough to sink to the bottom. Hence, the convective process generally can only reach some intermediate depths resulting in a layer of weak salinity minimum (about 34.45). Below that layer, there is the Sulu Sea Deep Water (SSDW) homogeneously distributed from 1 200 m down to the sea floor, of which the salinity is only a bit higher (about 34.46) above the minimum. Observational evidence shows that hydrographic conditions near the entrance of the MS in the SCS vary significantly from season to season, which make it possible to provide the MS-PS overflow with denser water of higher salinity sporadically. It is hence proposed that the SSDW is derived from intermittent deep convection resulted from property changes of the MS-PS inflow.
      根据历史观测研究了苏禄海的“通风”(ventilation)过程,并论及其盆间交换。其结果表明在近表层,苏禄海的海水更新过程不仅经由民都洛海峡和锡布图海峡发生,而且有赖于太平洋经苏里高海峡和保和海入流和南海经巴拉巴可海峡的入流。这两支入流似乎终年持续,其输运恐难以忽略。在表层下方,副热带次表层水(SLW)的核心层位于约200 m处,可经民都洛海峡不受地形阻挡地进入苏禄海。另一方面,尽管深度足以令其通过,并无SLW经锡布图海峡流入的迹象。苏禄海最值得注意的通风过程是发生在200 m至大约1200 m间的中深度对流。该对流系民都洛-班乃海峡准稳态入流所驱动,并受其支配。由于侵入的水体来自南海之北太平洋中层水(NPIW)的上部,它的密度通常不足以使之沉到海底。因此,其对流过程一般仅及某一中间深度,导致一不起眼的盐度极小值层(约34.45)。在该层之下(从1200 m直至海底)则是均一的苏禄海深层水(SSDW),其盐度仅略高于极小值(约34.46)。有观测证据显示,在民都洛的入口附近,南海的水文条件季节差异显著,使之有些时候会提供给民都洛-班乃海峡入流以密度较高的海水。因此推测,SSDW乃来自民都洛-班乃海峡入流水体性质变化所导致的间歇性深对流。
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