On the trapping of energy from storm surges on the coasts of the Sea of Okhotsk

Long wavelength surface-gravity waves, expressed as storm surges, are investigated in the context of whether they can transfer their energy into short-period seiches and edge waves to create unusually hazardous conditions along coastlines. To expedite the study a long-duration data set of sea level fluctuations obtained in the coastal zone of Sakhalin Island and the southern Kuril Islands is used, which employs bottom-mounted pressure transducers sampled every second. Tides and oscillations of less than 1 min period were eliminated from the extracted time series by filtering. Specifically, six fragments of time series containing storm surges with amplitudes greater than 20 cm are analyzed and discussed, exploiting the Korteweg–de Vries equation to show that the observed storm surges have an approximately cnoidal profile. Examination of the spectra for the selected fragments of each time series as the storm surges recede shows an increase in energy level in the 1–10 min period range and from 1 to 40 min period for some cases. To explain this effect, several pathways are conjectured that can potentially transfer energy from storm surges to seiches and edge waves, recognizing that no single process will act in all circumstances and that, whilst relevant to storm surges in general, the efficacy of each pathway will depend on the local coastal geometry and the hydrodynamics and ferocity of the storm surge.