Episodic circulation and exchange in a wave-driven coral reef and lagoon system
Episodic circulation and exchange in a wave-driven coral reef and lagoon system
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DOI：
10.4319/lo.2008.53.6.2681
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发表时间：
2008-11-01
影响因子：
4.5
通讯作者：
Monismith, Stephen G.
中科院分区：
文献类型：
--
作者：
Hench, James L.;Leichter, James J.;Monismith, Stephen G.
我们研究了在珊瑚礁-泻湖系统中，波浪驱动的环流相对于风和浮力的作用。在南部夏季，法属波利尼西亚莫雷亚州的泡保湾的环流测量表明，波浪在推动水流越过礁顶、穿过泻湖并流出礁口方面发挥了重要作用。潮汐相对较弱，由于接近两相点，并表现出一个不寻常的春季小潮周期，其中主要的月潮调节主要的太阳潮，并且整个潮相保持大致恒定。与表面波浪相比，风的作用只是次要的。简单的流体质量平衡表明浅层后礁快速冲刷并通过礁口出口，礁捕获带宽度约为2.3 km。岛礁通道环流动力学在波浪小时表现为两层斜压交换流，在波浪大时被抑制。异常微弱的潮汐强迫为更密切地研究波浪驱动的环流动力学提供了机会。正如理论上所预期的那样，在浅水泻湖上有一个波浪驱动的自由表面，它驱动了一个高度摩擦的流动，明显的是一个大的阻力系数C-D接近0.1。与现有理论不同的是，观测到的设置随着波高和周期的显著变化而发生强烈变化。总体而言，该珊瑚礁系统与邻近公海之间的环流和交换在很大程度上是由偶发的远程强迫事件决定的，与周期性的潮汐交换机制有很大不同。
We examined the role of wave-driven circulation relative to wind and buoyancy forcing in a coral reef-lagoon system. Circulation measurements in Paopao Bay, Moorea, French Polynesia, during austral summer show the importance of waves in driving flows over the reef crest, through the lagoon, and out the reef pass. Tides were comparatively weak, due to proximity to amphidromic points, and exhibited an unusual spring-neap cycle where the major lunar tide modulated the major solar tide, and the overall tidal phase stayed approximately constant. Wind had only a secondary effect compared to surface waves. A simple fluid mass balance indicated rapid flushing of the shallow back reef and export through the reef pass, and a reef capture zone width of similar to 2.3 km. The reef pass circulation dynamics exhibited two-layer baroclinic exchange flow when waves were small, which was suppressed during large wave events. The unusually weak tidal forcing provided an opportunity to more closely investigate wave-driven circulation dynamics. As expected theoretically, there was a wave-driven setup of the free surface across the shallow lagoon, which drove a highly frictional flow, evident by a large drag coefficient C-D approximate to 0.1. Diverging from extant theory, the observed setup varied strongly with significant wave height and period. Overall, the circulation and exchange between this coral reef system and the adjacent open ocean were largely determined by episodic remote-forcing events and differed significantly from periodic tidal-exchange mechanisms.