Internal wave observations in the Petacalco canyon, México

Abstract

This study presents the observation of large amplitude internalwave activity, of the order of 50 m, near the head of the Petacalco submarine canyon located in theMexican Pacific. The waves propagate with periods similar to the M2 tide component and the observations show that the rates of change of temperature reached up to 10 °C/hr. The presence of submarine canyons enhances turbulent mixing locally. The slopes of the canyon’s wall trap the waves as they propagate up-canyon. Based on linear wave theory, along the axis slope of the Petacalco canyon there are regions where the critical refraction is reached, suggesting that there are regions favorable for wave breakage. This process enhances mixing of cold water masses with shelf hot water. Through this mechanism, the mixed waters remain near the surface for longer periods of time, resulting in an alternative process to upwelling. Additionally, it is suggested that this process may be very important in the region since the winds there are very weak and do not support wind driven upwelling transport for most of the year.