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Temperature measured at the Monterey Inner Shelf Observatory (MISO) in southern Monterey Bay reveals frequent solitons and semidiurnal internal tidal bores (ITBs). A field study was undertaken to determine whether these features originate offshore and propagate shoreward over the continental shelf, and to characterize their evolution as they propagate. We developed a new survey method of using an autonomous underwater vehicle (AUV) to tightly track the thermocline along a 4.5 km transect, repeated 18 times over 18 hours, thereby measuring the internal-wave induced isotherm displacement at very high resolution. AUV measurements were compared with measurements at MISO, which is closer to shore. Internal waves of various scales were captured. An ITB of amplitude greater than 20 m propagating shoreward from the outer bay was the dominant feature. Rapid changes in stratification, possibly due to horizontal advection, were also observed. Technical challenges, advantages, and future improvements of this new AUV survey method are discussed. This study demonstrates that AUVs are efficient tools for surveying internal tidal waves.

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No abstract

The paper presents a performance analysis of a wave-energy converter designed for oceanographic applications to generate 300–500 W of electrical power on average. The prototype consists of a small draft cylindrical buoy connected to a submerged anti-heave plate by a hydraulic power takeoff system and cable. Engineering details and design of the system are based on the results of a detailed time-domain hydrodynamic analysis of the system, discussed here. The performance of the prototype is assessed with respect to the submerged plate size/added-mass and the effectiveness of latching schemes. Additionally, results for the power extraction are statistically compared with measurements performed during field tests in Monterey Bay, California. During these tests performance measurements were logged by the buoy, and wave data was recorded by a measurement buoy positioned 1 km from the deployment site. This allows the comparison of actual performance to model predictions run for the sea state present during testing. In general, the results of the numerical model match fairly well with the data acquired in field testing. The proposed causal latching control schemes have been shown to be ineffective for this type of wave-energy converter.