An accurate description of internal tides is a basis for understanding oceanic dynamic processes. This issue has become particularly important after the launch of the Surface Water and Ocean Topography (SWOT) satellite, which provides high-resolution sea surface height observations. Altimeter-derived coherent internal tides are widely used in current studies. However, under the influence of multiple generation sites and background flow, internal tides may lose coherence. To what extent coherent internal tides can represent the actual internal tide field remains unclear. Seamounts are ubiquitous in the global ocean. Caiwei Guyot, located in the western Pacific Ocean, is the third largest guyot on Earth and forms part of the Magellan Seamounts, making it a representative site for studying internal tides in a seamount-chain environment. In this study, the characteristics of internal tides are investigated by using long-term ADCP moorings as well as other supplementary observations.
Internal tides are significant at Caiwei guyot. Energy peaks can be seen clearly in D₁ and D₂ band at all stations, while D₂ energy dominates. Spring-neap cycle is predominant, while seasonal variation is weak. Near-critical slopes occur along the edge of the summit, favoring local internal tide generation. As the moorings are close to the edge, internal tides are expected to be mostly coherent, that is, the internal tides should be phase-locked to the local astronomic tide. However, the incoherent D₂ internal tides are comparable to coherent one, while incoherent D₁ internal tides has energy far exceed the coherent part.
Located at the Magellan Seamounts, internal tides from other seamounts can affect Caiwei guyot. The energy flux of coherent internal tides is aligned with the guyot's topography, indicating its local generation. The incoherent internal tides energy flux is highly variable, while most of it is consistence with the map shown by altimeter. By modifying the bottom pressure anomaly and its phase relationship with the barotropic tide, remotely incident internal tides can strongly modulate the local conversion rate. These findings highlight the importance of considering remote internal tides when studying internal tide dynamics over seamounts. Since incoherent internal tides may be dominant, further efforts are needed to extract and diagnose incoherent internal tides from altimeter such as SWOT, which will improve our understanding of ocean dynamics under complex conditions.

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