The first part of the talk will be dedicated to present the measurement infra-structure of TAU’s MEPLab in order to advance the our knowledge on waves and currents in the East Mediterranean region. The second part of the talk will present works on the topic of infra-gravity waves related to harbour agitation and waves of even lower frequencies, which relate to shelf- and bay-scale oscillations.
Infra-gravity waves are waves that lie outside of the wind-wave spectral regime. They are related to longer wave periods of few tens to few hundreds of seconds. Even though their wave heights are an order of magnitude lower than the ones in the wind wave spectral peak, their comparably large wavelengths (O(1-10km) depending on the bottom depth) can largely influence marine conditions due to basin resonances, harbour agitations and their influence on beach morphology. Their primary generation mechanisms are related to shoaling and breaking of the nearshore wave field. Thus, the focus of most previous related works has been limited to coastal areas. Based on the analysis of pressure cell measurements, we show evidence of IG wave generation by deep sea storms and present a new mechanism connecting seemingly unrelated phenomena of the comparably slow wind gusts and very fast IG waves. A simulation of IG wave generation, combining reflection of nearshore generated IG waves and deep water generation, shows good agreement with deep water measurements in the Pacific.
Sea level elevation observations ADCPs, tide gauges and wave staves indicate the existence of persistent low-frequency oscillations on the Israeli continental shelf. The dominant frequencies are shown to be consistent with extremely high nonlinear nearshore tide harmonics and shelf resonance models. A shallow water numerical model of Haifa Cape to Achziv shelf edge shows that this constellation enables energy trapping and occurrence of resonating standing waves. It has been found that the resonance periods fit also the ones of tsunami and metro-tsunami events with capability to deep-to-shallow signal increase of up to two orders of magnitude indicating Haifa Bay and Naharia areas to be extremely vulnerable to such events.