Synoptic Variability of the Currents in the Gotland Basin
of the Baltic Sea

E. A. Zakharchuk and N. A. Tikhonova

St. Petersburg Branch of the Zubov’s State Oceanographic Institute, St. Petersburg, Russia

e-mail: spb.soi@yandex.ru

Received September 18, 2011; in final form, May 31, 2012

Abstract—The series of long-term observations of synoptic-scale currents obtained by instrumental measure-
ments at the moorings in the Gotland Basin of the Baltic Sea are analyzed. The results of the statistical analysis
of the currents reveal their wave structure. The characteristics of the low-frequency waves received on the basis
of the cross-spectral analysis show that, in the range of periods from 2 to 20 days, they propagated in the south-
western, southeastern, and northwestern directions with phase speeds of 0.02–2.08 m/s and have lengths from
28 to 431 km. It is suggested that the distinguished wavelike perturbations of the synoptic-scale currents are
related to topographic waves. The analysis of the meteorological conditions and the results of the numerical
hydrodynamic modeling of the Baltic Sea free low-frequency fluctuations led us to conclude that the most pos-
sible mechanism of the generation of the intense wave-like oscillations of synoptic-scale currents in the Gotland
Basin is the resonance between the anemobaric forces and the relatively slow-moving anticyclones over the
open Baltic Sea and the eigenmode of the basin.

DOI: 10.1134/S0001437013030119

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