An Alternative Framework to Assess Marine Ecosystem Functioning in Shelf Seas (AlterEco) Primary productivity estimates derived from ocean glider in situ sensors and photosynthetically available radiation estimates from in situ and satellite data between November 2017 and May 2019 in the North Sea.

As part of the Alternative Framework to Assess Marine Ecosystem Functioning in Shelf Seas (AlterECO) project (NERC grant reference NE/P013902/1), Seagliders and Slocum gliders were deployed in a physically dynamic region of the North Sea, known to undergo seasonal oxygen depletion, between November 2017 and May 2019. These deployments are part of an 18 month observational programme using marine autonomous vehicles. During each deployment the gliders tracked repeat North-South or East-West transects close to Dogger Bank. Each glider carried a standard CTD package measuring temperature and water conductivity (salinity) and an oxygen optode sensor with additional sensors such as downwelling PAR and optical sensors for chlorophyll fluorescence and backscatter deployed for some missions. In this dataset, estimates of primary productivity are calculated from glider deployments carrying optical sensors for chlorophyll fluorescence, using the method described in Loveday et al. (2021), a modification of that presented in Hemsley et al. (2015). For glider deployments carrying an in situ downwelling PAR sensor, primary productivity is calculated. Primary productivity is also calculated for all glider deployments using Earth observation-based PAR derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) daily product. The variables in each file consist of; corrected in situ PAR, quenching corrected chlorophyll, mixed layer depth, euphotic depth, depth resolved estimates of primary productivity and depth integrated primary productivity. The chlorophyll fluorescence and PAR data are recorded at a lower sampling frequency when compared to the CTD sensor. Therefore, chlorophyll and PAR data values have been linearly interpolated onto the depth record time base. During the 3-year programme, and by developing and implementing a novel monitoring framework, AlterEco aims to deliver an improved spatio-temporal understanding of shelf sea function and provide measurements of critical indicators of marine ecosystem health over seasonal timescales.