Fundamental Adriatic seiche recorded by current meters

N. Leder (1) , M. Orlic (2)

1 Hydrographic Institute of the Republic of Croatia
2 Andrija Mohorovicic Geophysical Institute

Currents recorded at two stations positioned at the Adriatic shelf break between 17 February and 6 March 1989 were considered. They provided the first evidence of current variability related to the Adriatic-wide seiches. Current spectra were dominated by a peak at 21.1h ? a well-known period of the fundamental Adriatic mode. Amplitudes of oscillations were considerable, occasionally greater than 30cm/s. Both along- and cross-basin currents were recorded, thus signalling the importance of rotational effects. Comparison of the current data with the sea-level measurements performed simultaneously along the east Adriatic coast showed that the 21-h currents flowing in the Adriatic preceded sea levels by a quarter of a cycle, as would be expected from a simple model of bay seiches. Sea-level amplitudes reached 40cm in the North Adriatic, thus marking the event as one of the strongest on record. Seiching was triggered by a suddenly changing sirocco wind, as is usually the case in the Adriatic. The most important features of the seiche event were reproduced with a two-dimensional hydrodynamic model of the Adriatic Sea, forced by the sea-level residuals measured at Otranto and the air pressure and wind data recorded at Lastovo. The model showed that the seiche-related currents were relatively strong in the area where the current measurements were performed and further north ? between Zadar and Ancona.

Key words. Oceanography: general (continental shelf processes) ? Oceanography: physical (sea-level variations, currents)

Domaines: Océan, Atmosphère; Sciences de la Terre

N. Leder, M. Orlic. Fundamental Adriatic seiche recorded by current meters. Annales Geophysicae, 2004, 22 (5), pp.1449-1464. ⟨hal-00317319⟩