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Tidal Currents in the Northern Adriatic Sea: High Frequency Radar Observations and Numerical Model Predictions


C. Chavanne1, I. Janekovic2, P. Flament1,3, M. Kuzmic2, P.-M. Poulain4 and K.-W. Gurgel5
1 Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI 96822, USA.
2 Center for Marine and Environmental Research, Rudjer Boskovic Institute, Bijenicka 54, 10002 Zagreb, Croatia.
3 National Science Foundation, Division of Ocean Sciences, Arlington, VA 22230, USA.
4 Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Trieste, Italy.
5 Institute of Oceanography, University of Hamburg, Bundesstrasse 53, D-20146 Hamburg, Germany.


The results of a two-year long deployment of high frequency radars along the Italian coast of the northern Adriatic are analyzed, to characterize the surface tidal currents. M2 and K1 ellipses are aligned with the basin axis and exhibit large eccentricities in the middle of the basin, decreasing toward the Italian coast. Comparisons are made with a 3D finite-element non-linear numerical model of the tides. Complex correlations between modeled and observed tidal currents show a remarkable agreement in the middle of the basin, with magnitudes reaching 0.985 and average phases of 6:4. However the magnitudes drop to 0.5 within 20-30 km from the Italian coast, where the modeled currents amplitudes are underestimated by 2cm/s and the phases lag the observed phases by 60. This shallow region (less than 30-m deep) is characterized by low-salinity water originating at the Po River and laterally sheared coastal flows. The radars may have captured the influence of stratification or mean sheared flows, both absent from the model. The model parameterization of bottom friction may also inadequately represent the effects of real bottom friction on the vertical current shear.

Local Contact: (Klaus-Werner Gurgel)