Observations, modeling, and inter-comparison of waves from deep to intermediate waters in the East Mediterranean basin

Abstract

Wind waves are of great importance in various fields of oceanography and engineering. Although they propagate along entire seas and oceans, due to the complexity and high costs in setting deep water measurements, they are mostly measured only in nearshore regions. The connection between deep sea wave conditions and nearshore ones is commonly done using wave propagation models. Nevertheless, due to the scarcity of deep water measurements, the validity of this process is seldomly tested. This work presents newly acquired data for investigating wave evolution from the deep sea far beyond the continental shelf to intermediate coastal waters. The deep water wave measurements were obtained using an upward-looking Acoustic Doppler Current Profiler (ADCP) mounted on a submerged buoy (35 m depth) in the East Mediterranean 50 km offshore Israel (bottom depth of 1500 m). To the best of our knowledge, it is the first time that such a deep sea measurement is carried out in the region. Another ADCP was deployed on the sea bed (26 m depth) 2 km offshore. During this campaign, a substantial storm (Hm0=6 m) was recorded simultaneously by both ADCPs. A wave evolution model accounting for triad and quartet interactions was employed for connecting the two measurements, in order to explain the differences between the two measurements with numerical estimations. A new methodology was developed for resolving spatial variability in the deep sea conditions by assimilating the deep water data into the output of an operational wave model for the Mediterranean Sea. This allowed forming appropriate boundary conditions for propagation of the wave field from deep to coastal waters. Model results show an importance of accounting for inhomogeneity of the wave field in deep water. Nevertheless, the measurements indicate that one cannot expect to fully resolve the exact wave spectra only by applying wave modeling. This emphasizes the importance of conducting such deep wave measurements.