Optical remote sensing of coastal plumes and run-off in the Mediterranean region |
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Authors: | V Barale D Larkin |
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Institution: | (1) Space Applications Institute, Joint Research Center of the EC, 21020 Ispra (VA), Italy;(2) D.J.L. Software Consultancy Ltd, 63 Fellgate Av, Jarrow, NE32 4QR Tyne and Wear, UK |
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Abstract: | Sea surface colour data, derived from the Coastal Zone Colour Scanner (CZCS) archive, have been used to assess the space/time
variability of coastal plumes and run-off in the Mediterranean Sea. A time series of 2645 scenes, collected by the CZCS from
1979 to 1985, was processed to apply sensor calibration algorithms, correct for atmospheric contamination, and derive chlorophyll-like
pigment concentration. Individual images, remapped on a 1-km2 pixel grid, were generated for each available day, and then mean values calculated pixel by pixel to form monthly, seasonal
and annual composites. The results obtained must be taken with caution, due to the CZCS limitations in the quantitative assessment
of bio-optical pigments when high concentrations of dissolved organics or suspended sediments are present, e.g. along littorals
or within plumes. Marked differences appear in the distribution of water constituents between coastal zones and open sea,
northern and southern near-coastal areas, western and eastern sub-basins. The oligotrophic character of the basin contrasts
with areas of high concentration related to river plumes—Ebro (Ebre), Po, Rhone, Nile—, coastal run-off patterns, and persistent
mesoscale features (e.g. coastal filaments and eddies). Seasonal variability appears to be high, with higher concentrations
occurring over most of the basin in the cold season, when climatic conditions are favourable to coastal run-off and vertical
mixing. Atmospheric forcing (wind and rainfall over continental margins) could play an important role in establishing the
observed space/time distribution of water constituents. The impact of continental interactions (fluvial and coastal run-off),
or that of exchanges between coastal zone and open sea, could have paramount influence on the biogeochemical fluxes in the
entire basin. |
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Keywords: | Coastal zone River plume Sea surface colour |
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