Evidence of a coastal-shelf trapped wave in the Gulf of Tehuantepec

Generation and propagation of coastally trapped waves (CTW) is a well studied process. However, CTW observations are limited by instrumentation technologies and time-spatial resolution, hence its complete understanding still limited. In this work we use High-Frequency Radars (HFR) measurements to analyze the sub-inertial dynamics over the Gulf of Tehuantepec, Mexico, an area strongly influenced by gap-winds. The sub-inertial frequency domain showed oscillations that may be explained by CTW traveling towards the pole. These oscillations showed significant coherence (95% of confidence) with gap winds at the Gulfs of Papagayo and Panama, more than with local winds. Thermocline vertical oscillations, measured with a moored thermistor-chain, showed the same agreement with Papagayo and Panama winds. The period of the observed CTW is ~4 days (the inertial-local period for Panama Gulf). Data presented here suggests that inertial oscillations generated off Papagayo travels northward trapped to the coastal-shelf for about 1200 km and are detected as surface current pulses in the HFR installed at the Gulf of Tehuantepec. As showed by CTD profiles, these CTW could have an cross-shore scale of ~200 km with its upwelling core located at the shelf break. The possible relationship of CTW with local climate is discussed.