seanoe:98111 HUGUET Antoine Ifremer, Service Valorisation de l’Information pour la Gestion Intégrée Et la Surveillance, Rue de l’ïle d’Yeu, B.P. 21105, 44311 Nantes Cedex 3, France Antoine.Huguet@ifremer.fr 2024-06-26 ISO 19115:2003/19139 1.0 Map of Chlorophyll a concentrations trend between 1998 and 2019 in the Gulf of Biscay 2023-11-28 2024-06-26 Huguet Antoine (2023). Map of Chlorophyll a concentrations trend between 1998 and 2019 in the Gulf of Biscay. SEANOE. https://doi.org/10.17882/98111 For the 21 years of the study, an examination of trends in chlorophyll concentration revealed a general decline throughout the Gulf over the production period. These trends, extracted from dynamic linear model, also allowed this decline to be quantified. Expressed as a percentage, a large part of the area below the 50 m bathymetric line showed a decrease of at least 10% over the period, corresponding to a value of at least 0.1 µg.l-1. However, the spatial distribution reveals some more local phenomena. In southern Brittany, from Quimper to Vannes, a particular feature appears, with an upward trend over several kilometres along the coast, followed by a pronounced gradient along the coast. This gradient includes a zone where a continuous monotonic increasing trend is observed, then a zone where the trend becomes not significant and finally, about 15 km from the coast, a new zone where a significant continuous monotonic decreasing trend is observed. The increase in chlorophyll a concentration in the very coastal part is greater than 0.1 µg.l-1 over the period. Another peculiarity concerns the central part, located at the edge of the plateau at Cap Ferrat and Pente Aquitaine, where an increase in chlorophyll a was observed, but the variations remained small, being less than 0.1 µg.l-1. About a hundred kilometres south-west of Saint Nazaire, an area of about 40 by 50 km shows a decrease in chlorophyll a of more than 20%, quantified as more than 0.1 µg.l-1 over the period. SOUDANT Philippe BARILLE Laurent PETITGAS Pierre HUGUET Antoine Ifremer, Service Valorisation de l’Information pour la Gestion Intégrée Et la Surveillance, Rue de l’ïle d’Yeu, B.P. 21105, 44311 Nantes Cedex 3, France Antoine.Huguet@ifremer.fr SEANOE https://www.seanoe.org/data/00869/98111/illustration.gif Chlorophyll a dynamic linear model satellite time series climate change Environment Pigments ODATIS aggregation parameters and Essential Variable names 2024-09-16 geonetwork.thesaurus.external.theme.NVS.OD1 Environment SeaDataNet Parameter Disciplines 2021-04-07 geonetwork.thesaurus.external.parameter.NVS.P08 /Observational data/in-situ Type de jeux de donnée ODATIS 2024-10-15 geonetwork.thesaurus.local.theme.type_jeux_donnee CC-BY (Creative Commons - Attribution) oceans -7.915473 0.173522 40.457753 48.708403 1998-01-01 2019-12-31 CSV https://www.seanoe.org/data/00869/98111/data/107387.csv WWW:DOWNLOAD-1.0-link--download Processed data CSV file is constituted with 10 fields. Field P.Value is the result of Man kendall test (Yue et Wang), Résultat...VariationUnité is the variation of Chl a expressed in µg/l - 17 MB https://doi.org/10.17882/98111 WWW:LINK-1.0-http--metadata-URL DOI of the product https://www.seanoe.org/data/00869/98111/ rel-canonical Seanoe Times series have been constituted with daily MODIS satellite data. Chlorophyll a concentrations have been calculated for each pixel with OC5 algorihm (Gohin et al., 2002 ; Gohin, 2011).