Observations of wave‐generated vortex ripples on the North Carolina continental shelf
Observations of wave‐generated vortex ripples on the North Carolina continental shelf
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DOI：
10.1029/2001jc000986
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发表时间：
2002-10
影响因子：
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通讯作者：
F. Ardhuin;T. G. Drake;T. Herbers
中科院分区：
文献类型：
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作者：
F. Ardhuin;T. G. Drake;T. Herbers
[1] 在 1999 年 9 月和 12 月进行的 3 次侧扫声纳调查中，在北卡罗来纳州附近的美国东海岸大陆架底部观察到波长在 0.5 至 3 m 之间的沙波纹。大约 75% 的调查图像中出现了波纹，特别是在沉积物较粗的区域。对表面沉积物样品的分析表明，中值粒径范围为 0.1 至 4.7 毫米，内陆架在距离 <1 公里内变化较大。观察到的波纹特性与波产生的涡旋波纹一致。对同时波观测的分析表明，波纹波峰的排列垂直于先前事件期间近底部波浪引起的运动的平均方向，这些运动的能量足以动员表面沉积物。此外，波纹波长与近底波轨道偏移的比例与波形涡旋波纹一致。这些发现支持这样的假设：观察到的跨大陆架的波浪强烈衰减是由大涡旋波纹上的形状阻力造成的。
[1] Sand ripples with wavelengths between 0.5 and 3 m were observed on the bottom across the U.S. east coast continental shelf off North Carolina during three side-scan sonar surveys in September and December 1999. Ripples were present in about 75% of the survey images, in particular, in regions with coarser sediments. Analysis of surficial sediment samples shows that median grain diameters range from 0.1 to 4.7 mm with large variations on the inner shelf over distances <1 km. The observed ripple properties are consistent with wave-generated vortex ripples. Analysis of concurrent wave observations indicates that the ripple crests were aligned perpendicular to the average direction of near-bottom wave-induced motions during preceding events that were sufficiently energetic to mobilize surficial sediments. Furthermore, the ripple wavelengths proportionality to near-bottom wave orbital excursions is consistent with wave-formed vortex ripples. These findings support the hypothesis that the observed strong attenuation of waves across the shelf resulted from form drag over large vortex ripples.