Variability of Adriatic Sea coastal turbid waters from SeaWiFS imagery

The objective of this work is to gain new insight on the variability and offshore export of turbid coastal waters in the Adriatic Sea, which are optically classified as Case 2 waters. This is done by means of the 1998-2004 SeaWiFS ocean color products (chlorophyll, Case 2 flags and light attenuation coefficient at 490 nm, k(490)) and NOAA AVHRR sea surface temperature. The role of wind-driven circulation in the redistribution of the above ocean color features is also analyzed both at seasonal and interannual time scales and in the light of particular wind and current situations occurring in 2003, via scatterometer wind data as well as atmospheric and marine circulation medium and high resolution model output. Results indicate that turbid (Case 2) waters are exported offshore at the Po delta and Ancona headland during the colder months, in concomitance of Bora wind events and when the 2003 daily Po river discharge is above about 500 m(3) s(-1) and 1000 m(3) s(-1), respectively. Southeasterly Sirocco events do not to originate extensive offshore transport, but only locally modify the shape of the WAC front. Mistral episodes enhance the WAC flow into the Ionian Sea. Finally, estimates of coastal current width and length from Case 2 flag distribution follow the Po discharge pattern, confirming this forcing to be the main responsible for WAC width seasonal modulation. Experimental WAC widths agree reasonably with theoretical analyses, while underestimation of WAC length suggests the necessity to include the other Italian rivers in the freshwater discharge evaluation.