Exploring Physical and Biogeochemical Variability in the Southeast Bay of Biscay: insights from a glider mission and the analysis of complementary multiplatform data

Keywords: Glider, Biogeochemical status, Multiplatform observations, Coastal Monitoring, Blue Economy Hub A 11-day glider mission was conducted in November 2023 in the SE Bay of Biscay. The glider was equipped with hydrographic and biogeochemical sensors, measuring temperature, salinity, turbidity, fluorescence, dissolved oxygen, CDOM, and nitrates. Additionally, it estimated integrated currents within the water column. These data were shared in real-time with the global Operational Oceanography community through collaboration with Coriolis DAC (Data Assembly Centre) and OceanOPS (WMO-IOC Support Center for in-situ observation programs of oceanography and marine meteorology). The monitored area encompassed the continental shelf and the upper slope of the Basque Country coast, which is covered by Copernicus Marine Service in-situ data from the EuskOOS observatory (https://euskoos.eus/mapv2/), including a HF radar and one slope buoy. In this work, we show the physical and biogeochemical variability related to a marked river plume event at an unprecedented spatio-temporal resolution, emphasizing the potential of combining in-situ, remote, and model data for effective coastal monitoring. During the mission, intense currents towards the W-SW favoured the westward extension of the Adour River plume, which resulted in low salinities and nitrate surface anomalies measured by the glider, coherent with the few available satellite data and model simulations from the Copernicus Marine System. This study is the first step for an enhanced observatory in the study area devoted to new services tailored for the coastal ocean user’s community, in the framework of the ongoing Oarsoaldea Blue Economy Hub initiative (https://www.azti.es/en/blue-economy-to-boost-oarsoaldea/).