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Abstract
A new method (the ‘sink’ method) is proposed for the mapping of productive mesoscale oceanic thermal fronts based on the combined analysis of satellite imagery for sea surface temperature (SST) distribution and chlorophyll (CHL) concentration under a Geographic Information System (GIS). In an SST lattice data array, data value sinks describe heterogeneous drops in SST distribution as this is compared to more homogeneously distributed SST in the surrounding area. Using Arc/Info GIS, these thermal discontinuities are flagged and applied on SST and CHL imagery for the calculation of differences in SST and CHL patterns (DSST and DCHL) inside and outside of these flagged areas. Spatially connected sinks that are characterized by simultaneous negative DSST and positive DCHL pattern are mapped as thermal fronts. Results include a time series of monthly front occurrence GIS maps in Eastern Mediterranean waters along with three calculated front characteristics (DSST, DCHL and bathymetry). Comparisons between the mapped fronts and isobath distributions present clearly visible front‐to‐isobath spatial and shape associations while spatial analysis between front and wind data explains 66% of the number of mapped fronts.
Acknowledgements
This work was partly funded by a European Communities (Fifth Framework Programme) research project (CEPHSTOCK QOL‐2001‐5.1.2) and a Hellenic Secretariat of Research and Technology (Ministry of Development) project (IMAS E2050‐5/1). The authors thank the SeaWiFS Project and the Distributed Active Archive Centre at the Goddard Space Flight Centre, Greenbelt, MD 20771, for the production and distribution of SeaWIFS data, the German Aerospace Agency for the distribution of AVHRR data as well as two anonymous referees for constructive comments on the manuscript.