SEA-LEVEL OSCILLATIONS WITH SUPER-TIDAL FREQUENCY IN A COASTAL EMBAYMENT OF WESTERN NORWAY

In a coastal embayment near the headland Stad in the northwest of Norw ay, recent measurements of sea water current and sea level revealed pe rmanent barotropic oscillations with a mean period of 48 min. The sea level oscillations that are superimposed on the signal of the dominati ng semi-diurnal tide have a mean range of 3-5 cm, while maximum observ ed values exceed 20 cm. The character of the oscillation is different from numerously reported bay oscillations and seiches of comparable pe riod, which are all transient. In this paper these observations are pr esented and analysed. Possible artifacts caused by sampling or analysi s are investigated, and may be ruled out as an explanation. Due to its permanent character, the only possible energy source for the oscillat ions seems to be the regular semi-diurnal tide or one of its dose cons tituents.