High-frequency oscillations observed in the Krka Estuary

Current and temperature data, taken during 1986 and 1987 in the Krka Estuary (east Adriatic coast), are analysed for evidence of high-frequency oscillations. The spectra computed from the data show peaks at 0.006 and 0.022 min −1 (corresponding to periods of 2.8 h and 45 min, respectively). Detailed analysis of the 45-min oscillations in both time and frequency domains reveals that these oscillations occur intermittently. They probably represent internal waves travelling down the estuary. The waves appear to be generated by the interaction of the second-order surface seiches with topography. The system of coupled surface seiches and internal waves may be either of local meteorological origin or externally forced at the mouth of the estuary.