We present an extensive analysis of the first complete data set in the
northern Ionian Sea collected during the Physical Oceanography of the
Eastern Mediterranean (POEM) general circulation survey of September
1987. A four water mass structure of the basin is found to be represen
ted by a first internal baroclinic Rossby radius of deformation of 11.
8 km. The horizontal correlation scales decrease with depth, and the s
ubsurface flow is dominated by anticyclonic gyres. Large-scale circula
tion trends of the temperature and salinity covariance matrices are co
mpensated below 200 m, and only the gyre scales (approximately 100 km)
persist at intermediate and deep levels. The empirical orthogonal fun
ctions of the data set show that an horizontal scale separation exists
between the first and higher vertical modes of the dynamic height fie
ld.