Tidal oscillations dominate the flow field in many submarine canyons. Observations have shown that semidiurnal tidal energy in submarine canyons is significantly amplified with respect to adjacent shelves. This amplification is thought to be caused by focusing of propagating internal tides incident from the open ocean, or local in‐canyon generation on critical canyon floor slopes. These mechanisms require freely propagating internal tides, with superinertial frequencies. We present results from a moored array in a canyon at 44°N, where the observed velocities reached over 0.8 m s~(-1). The canyon flow field was highly unusual because it was dominated by the subinertial diurnal tide. This occurred despite the fact that the barotropic tide was predominantly semidiurnal. The diurnal tide was dramatically amplified in the canyon, its velocities increasing toward the seafloor and canyon head. The diurnal oscillations also exhibited marked modulation in time by the background barotropic forcing. Length scales suggest that the diurnal tide should be resonant in the canyon. An analytical framework is used to explain the mechanisms behind the strong diurnal currents observed by the moored array. In the model, along‐shelf barotropic flow sets up a double Kelvin wave response in the canyon, generating along‐canyon velocities which are subsequently amplified by resonance. The pattern of the model predictions is in excellent agreement with the observed velocity pattern.
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机译：潮汐振荡主导着许多海底峡谷的流场。观测结果表明，海底峡谷中的半日潮汐能相对于相邻的架子明显放大。据认为，这种放大是由于集中在从公海传播的内部潮汐或在关键的峡谷底坡上的局部峡谷内生成引起的。这些机制需要以超惯性频率自由传播内部潮汐。我们提出了在44°N的峡谷中系泊阵列的结果，其中观测到的速度超过0.8 m s〜（-1）。峡谷流场非常不寻常，因为它主要受惯性昼间潮汐支配。尽管正压潮主要是半昼间的，但还是发生了这种情况。日潮在峡谷中急剧放大，其向海底和峡谷顶部的速度不断增加。昼夜振荡还通过背景正压强迫在时间上表现出明显的调制。长度刻度表明，昼夜潮应在峡谷中共鸣。使用分析框架来解释由停泊的阵列观测到的强大的昼夜水流的机理。在该模型中，沿陆架的正压流在峡谷中建立了双开尔文波响应，产生沿峡谷的速度，随后该速度通过共振放大。模型预测的模式与观测到的速度模式非常吻合。
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