Pressure‐forced seiches of large amplitude in inlets of the Balearic Islands: 2. Observational study

Abstract

In part 1 of this study, Gomis et al. [1993] proposed a possible mechanism for the generation of large‐amplitude seiches observed in inlets of the Balearic Islands. In part 2, we revise the proposed mechanism in light of recent observations. These consist of simultaneous records of sea level/bottom pressure measured at three locations inside and outside Ciutadella inlet and atmospheric pressure measured at four sites inland nearby. First, results that support the existence of offshore surface waves of atmospheric origin are shown. Next, a detailed analysis of atmospheric data reveals the passage of non dispersive waves with a predominant direction and phase speed that seem to be about the same during seiche events. Finally, coherence, phase difference, and admittance functions estimated for different pairs of instruments are compared with the theoretical results. All observations indicate that large‐amplitude seiches observed in Ciutadella are likely the result of a resonant coupling between offshore surface waves generated by atmospheric disturbances and the fundamental mode of that inlet, as suggested in part 1. However, the analytical model used in part 1 is clearly too simple to explain the observed characteristics of the offshore surface waves.