Oceanologia (Jun 2006)
Periodic variability of currents induced by topographically trapped waves in the coastal zone in the Gulf of Finland
Abstract
The aim of this paper is to examine the water exchangeregime between the bays of northern Estonia (Pakri Bay, IhasaluBay and Muuga Bay) and the open part of the Gulf of Finland.To this end, the current measurements and CTD-castings performedat the border of the bays and the open part of the Gulf of Finlandin summer 1994, 1995-96 and 1997 are analysed. All the currentmeasurements displayed one feature in common: the existence ofperiodic variability with a current amplitude of between 5 and25 cm s-1 and a variability period of 3-4 days (68 hours in PakriBay, 72 hours in Muuga Bay and 78 hours in Ihasalu Bay). Theamplitudes of this variability differed during different timeperiods of the experiment and in different parts of the southernGulf of Finland. The hypothesis was propounded that this variabilityis the result of bottom-trapped waves, as had been found in manyother regions of the Baltic Sea (Aitsam & Talpsepp 1982, Talpsepp1983). To interpret the results of the measurements, a modelof bottom-trapped waves for this region was used. This was theshort-wave version of Huthnance's (1978) numerical model of coastal-trappedwaves, according to which the wave parameters for the experimentalregions were calculated. Comparison of the model and the measurementsimplies that coastal-trapped waves do exist off the southerncoast of the Gulf of Finland.
