Description: Two Slocum gliders (units 331 and 439) were deployed during RRS Discovery expedition DY081 on July 17th 2017 at 62.9°N, 52.6°W, approximately 40 km off the Greenland shelf break, travelled North along the coast in a zig-zag pattern between the shelf and deep waters, and were recovered 8 days later from 63.7°N, 53.1°W and 62.9° N, 52.7°W respectively on July 24th 2017. Gliders profiled from the surface to 1000 m, except during the two excursions onto the shelf, once south and once north of the Godthåb Trough, where they followed the bathymetry. Each glider was fitted with a pumped CTD and bio-optical sensors (WET Labs puck). These bio-optical sensors measure optical backscattering (in the form of volume scattering function), chlorophyll fluorescence, and UV fluorescence for fluorescing dissolved organic matter (FDOM), a subset of coloured organic matter (CDOM). This dataset contains raw and processed/gridded data files from the glider deployments. The raw data are contained as .dbd and .ebd files in ***_raw_data.zip folders for each of glider unit 331 and 439. The data were processed using the SOCIB glider toolbox (https://github.com/socib/glider_toolbox) and saved as a NetCDF (processed_***.nc) with the following variables: longitude, latitude, time (Julian Day), pressure, eastward velocity, northward velocity, temperature (not thermally corrected), salinity (not thermally corrected), chlorophyll fluorescence (not corrected for quenching), coloured organic matter (cdom), backscatter (volume scattering function) and oxygen concentration. The expedition report is provided and metadata can be found in the processed/gridded data files.

Description: We contend that ocean turbulent fluxes should be included in the list of Essential Ocean Variables (EOVs) created by the Global Ocean Observing System. This list aims to identify variables that are essential to observe to inform policy and maintain a healthy and resilient ocean. Diapycnal turbulent fluxes quantify the rates of exchange of tracers (such as temperature, salinity, density or nutrients, all of which are already EOVs) across a density layer. Measuring them is necessary to close the tracer concentration budgets of these quantities. Measuring turbulent fluxes of buoyancy (Jb), heat (Jq), salinity (JS) or any other tracer requires either synchronous microscale (a few centimeters) measurements of both the vector velocity and the scalar (e.g., temperature) to produce time series of the highly correlated perturbations of the two variables, or microscale measurements of turbulent dissipation rates of kinetic energy (ϵ) and of thermal/salinity/tracer variance (χ), from which fluxes can be derived. Unlike isopycnal turbulent fluxes, which are dominated by the mesoscale (tens of kilometers), microscale diapycnal fluxes cannot be derived as the product of existing EOVs, but rather require observations at the appropriate scales. The instrumentation, standardization of measurement practices, and data coordination of turbulence observations have advanced greatly in the past decade and are becoming increasingly robust. With more routine measurements, we can begin to unravel the relationships between physical mixing processes and ecosystem health. In addition to laying out the scientific relevance of the turbulent diapycnal fluxes, this review also compiles the current developments steering the community toward such routine measurements, strengthening the case for registering the turbulent diapycnal fluxes as an pilot Essential Ocean Variable.