Some results of drift card experiments in the Adriatic during the period 1979-1980
Abstract
The drift card experiment was carried out between January 1979 and July 1980. in order to study surface circulation of the Adriatic Sea.
In all, 9.245 drift cards were released et 128 stations and 1279 (i.e. 15.8%) were recovered. This percentage of recoveries is the usual one when this kind of experiments is carried out in rather large aquatic areas.
Recovered drift cards yielded the information on the probable courses they have followed as well as on current directions for four seasons.
Result were compared with the direct current measurement data (from some of the Adriatic stations), as well as with gradient current calculations for different situation. Results showed good agreement with both direct current measurement data and gradient current calculations.
This experiment gave the qualitative and quantitative characteristics of surface layer circulation by seasons. Cyclonic current flow was established in all seasons, with the highest intensity in winter - autumn and considerably lower intensity in summer. Transversal E-V and W-E flowe were also recorded in all seasons. However, they varied considerably with respect to their intensity and direction. Transversal flowes of W-E direction were considerably less intensive and occured only in spring.
Data on current speeds obtained by this experiment are not quite reliable due to the boor knowledge of actual drift card trajectories. Nevertheless, some surface flow properties could be inferred from the data obtained by the cards recovered relatively shot time after they were released (3 - 5 days).
Speeds of cyclonic flow currents ranged between 0.2 and 0.5 knots. Transversal current flow had the speed of 0.2 - 0.8 knots.
Inflow current speeds of 0.8 knots were recorded in winter - autumn, while outgoing current speeds ranged between 0.5 - 0.7 knots.
