The MAREL (Mesures Automatisées en Réseau pour l’Environnement Littoral) Carnot system developed and implemented by Ifremer (French Research Institute for Exploitation of the sea) in 2004 is a moored buoy equipped with physico-chemical and biological measuring devices working in continuous and autonomous conditions. The system is located at the entrance of Boulogne-sur-Mer harbor (eastern English Channel) which is influenced by marine and fresh waters. The measuring station is equipped with high performance systems for seawater analysis and near real time data transmission. This system records with a high temporal resolution (20 minutes) the following parameters: estimated sea level, gust wind speed, gust wind direction, wind from direction relative true north, horizontal wind speed, relative humidity, light irradiance surface PAR, sea temperature, practical salinity, pH, dissolved oxygen, fluorescence, turbidity. For nitrate + nitrite, phosphate, silicate parameters the sampling frequency is set to 12 hours. For each variable, the name of the related sensor and its implementation period are proposed in the table below. More information on metadata, Quality Control procedures, pre-processing and processing steps, related scientific works based on the MAREL Carnot data are available from Halawi Ghosn R. & Lefebvre A. (2023) as referenced below. The MAREL Carnot system is a component of the national high frequency observing network COAST-HF link to the Research Infrastructure IR ILICO.