Giant kelp (Macrocystis pyrifera) forests are common along the California coast. Attached on the rocky bottom at depths of approximately 5–25 m, the kelp, when mature, spans the water column and develops dense, buoyant canopies that interact with waves and currents. We present two novel results based on observations of surface gravity waves in a kelp forest in Point Loma, California. First, we report short wave (1–3 s) attenuation in kelp, quantified by an exponential decay coefficient —comparable to the dampening effect of sea ice. Second, we identify seasonal and tidal changes in attenuation, peaking mid‐summer with maximum kelp cover, and during low tide when a greater proportion of the fronds are at the surface. Thus, the naturally occurring surface canopies of kelp forests can act as temporally varying, high‐frequency filters of wave energy.

中文翻译：

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海带森林冠层的短波衰减

巨型海带（荧光大囊藻）森林在加利福尼亚海岸很常见。海带附着在大约 5-25 m 深处的岩石底部，成熟后会跨越水柱，形成致密、有浮力的冠层，与波浪和水流相互作用。我们基于对加利福尼亚州洛马角海带森林中表面重力波的观测，提出了两项​​新颖的结果。首先，我们报告了海带中的短波（1-3 s）衰减，通过指数衰减系数进行量化——与海冰的阻尼效应相当。其次，我们确定了衰减的季节和潮汐变化，仲夏时达到峰值，海带覆盖范围最大，而在退潮期间，更多的叶状体位于水面。因此，海带森林自然形成的表面冠层可以充当随时间变化的波能高频过滤器。