The Use of Ocean-Colour Data to Estimate Chl-a Trends in European Seas

摘要

Ocean-colour remote-sensing products have been used to estimate Chl-a trends in European seas with the aim to develop a new indicator based on ocean-colour data for the European Environment Agency (EEA). The new indicator, called CSI023(+), derived from satellite ocean-colour products from the MyOcean Marine Core Service (www.myocean.eu) has been defined and calculated. In our analysis, we have used 3 MyOcean satellite products: 2 global satellite products (SeaWiFS and a merged product) and one regional (adjusted to specific regional Mediterranean conditions) ocean-colour product. We have evaluated the differences among the 3 different products in estimating Chl-a trends. CSI023(+) complements the EEA CSI023 indicator for eutrophication based on chlorophyll-a (Chl-a) in-situ observations. Analysis has revealed the potential of ocean colour as a CSI023(+) indicator to detect large-scale, and in some cases, even local-scale, changes and decreasing trends of Chl-a were observed throughout the Black Sea, the Eastern Mediterranean, the southern part of the Western Mediterranean, the English Channel and the north part of the North Sea. Large areas with increasing trends were observed in the Bay of Biscay, in the North-East Atlantic regions of Ireland and the UK, in the northern part of the North Sea, in the Kattegat and in the Baltic. Specific analysis has been performed in the Mediterranean coastal areas using regional products to investigate local scale results. Validation of ocean-colour products has been carried out through comparison with observations of the Eionet EEA database. The validation results highlight that regional products produced with regional algorithms are recommended for the future.