ALBERT

Beschreibung: 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.

Beschreibung: Binned median of Slocum G2 glider data from 0 to 1000 m depth. The data were collected in the northern Benguela region between 14 February 2018 and 19 June 2018 at a site approximately 100 km from the coast. The glider sampled continuously following a triangular path of ~12 km per side roughly centred on 10.8°E, 18.1°S. The glider sampled only on the upward dive with a vertical resolution of ~20 cm, emerging 5 to 6 times per day. Temperature, Conductivity and Depth were measured with a standard Slocum Glider Payload CTD (pumped) from Seabird (SN 9109). Dissolved oxygen was measured with an Aanderaa optode, model 4831 (SN286). Depth-averaged currents (DAC) for each 1000 m downward and upward dive were estimated from the difference between the glider's actual and predicted surfacing locations. Glider surface currents were also estimated at each surfacing via linear regression of GPS location with respect to time. Salinity and oxygen data were calibrated against shipboard CTD bottle samples. The data have been binned (median) into 6 hourly, 2 m depth bins for all variables while the currents timeseries were binned daily (median). 1D variables consist of: time (seconds since 00:00:00 on 1 January 0000), depth (meters), longitude (degrees East), latitude (degrees South), zonal and meridional glider surface currents (U_surf and V_surf, m/s), and zonal and meridional glider depth averaged currents (U_dac and V_dac, m/s). 2D variables consist of: conservative temperature (°C), absolute salinity (g/kg), potential density (kg/m³), and dissolved oxygen concentration (µmol/kg).

Beschreibung: Physical, chemical and biogeochemical measurements derived from CTD-rosette deployments during three visits to site P3 (November to December, 2017) in the South Atlantic. Measurements were made during COMICS cruise DY086 on the RRS Discovery using a trace metal free Titanium Rosette (events 4, 7, 15, 19, 24, 26, 29) and a Stainless Steel Rosette (all other events). Physical parameters include temperature, salinity, density, photosynthetically active radiation and turbulence; chemical parameters include dissolved oxygen, dissolved oxygen saturation, nitrate, phosphate and silicate; biogeochemical parameters include turbidity, beam transmittance, beam attenuation, fluorescence, particulate organic carbon (POC), dissolved organic carbon (DOC), chlorophyll-a, net primary productivity (NPP), ambient leucine assimilation and bacterial cell count. To determine turbulence, a downward facing lowered acoustic doppler current profiler (LADCP, Teledyne Workhorse Monitor 300 kHz ADCP) was attached to the CTD frame. Shear and strain, which are obtained from velocity and density measurements, were used to estimate the dissipation rate of turbulent kinetic energy and the diapycnal eddy diffusivity from a fine-scale parameterisation. Estimates are calculated by parameterising internal wave-wave interactions and assuming that wave breaking modulates turbulent mixing. A detailed description of the method for calculating diffusivity from LADCP and CTD can be found in Kunze et al. (2006). Two datasets with different vertical resolutions were produced: one in which the shear is integrated from 150 to 300 m and the strain over 20-150 m, and one in which the shear is integrated from 70 to 200 m and the strain over 30-200 m. Nutrients (nitrate, phosphate, silicate) were determined via colourimetric analysis (see cruise report, Giering and Sanders, 2019), POC was determined as described in Giering et al. (2023), DOC and DOC flux were determined as described in Lovecchio et al. (2023), NPP was determined as described in Poulton et al. (2019), and ambient leucine assimilation and bacterial cell count were determined as described in Rayne et al. (2024). Bacterial abundance and leucine assimilation were made from bottle samples of six CTD casts of the stainless-steel rosette. Water was collected at six depths (6 m, deep-chlorophyll maximum, mixed layer depth + 10, 100, 250 and 500 m). Acid-cleaned HDPE carboys and tubing were used for sampling. Samples were then stored in the dark and at in-situ temperature prior to on-board laboratory sample preparation or analysis. Flow cytometry was used to measure bacterial abundance. Room temperature paraformaldehyde was used to fix 1.6 ml samples for 30 minutes. Then, using liquid nitrogen, the samples were flash frozen and stored at -80°C. Samples were then defrosted before being stained using SYBR Green I and run through the flow cytometer (BD FACSort™). The method of Hill et al. (2013) was applied to determine prokaryotic leucine assimilation using L-[4,5-³H] leucine which has a specific activity of 89.3 Ci/mmol­. In the mixed and upper layers of the water column, the protocol in Zubkov et al. (2007) was followed. Below the mixed layer, adaptions to the method included reducing the concentration of ³H-Leucine to 0.005, 0.01, 0.025, 0.04 and 0.05 nM; increasing experimental volumes to 30 ml; enhancing incubation times to 30, 60, 90 and 120 min. These adaptions were made to improve accuracy where lower rates of leucine assimilation were expected. Data were provided by the British Oceanographic Data Centre and funded by the National Environment Research Council.

Beschreibung: Dataset used in Henson et al. (2023). Binned, calibrated, merged glider data collected with 2 Slocum G2s and 1 Seaglider from 0 to 1000 m depth. The data were collected NW of South Georgia, Scotia Sea between 19 October 2017 - 13 February 2018. Gliders sampled continuously following a triangular path of ~12 km per side centred on 52.75°S, 40.16°W. The glider sampled with a vertical resolution of ~20 cm, emerging 5 to 6 times per day. Temperature, Conductivity and Depth were measured with a Seabird CTD (pumped) on Slocum gliders and a pumped Seabird CTD sail on the Seaglider. Dissolved oxygen was measured with Aanderaa optodes. Chlorophyll fluorescence and optical backscatter were measured using Seabird Triplet ECOPucks. Oxygen and chlorophyll data were calibrated against shipboard bottle samples collected using a CTD rosette. Chlorophyll data have been corrected for non-photochemical quenching. Optical backscatter was additionally converted into POC concentration using shipboard CTD bottle samples, and estimates of POC flux were then made following the methods detailed in Henson et al. (2023). Data from the 3 gliders were inter-calibrated prior to ship calibration. Estimates of primary production are made from the glider data and photosynthetic properties observed during a coincident cruise, following the methods of Mignot et al. (2018). The 2D glider profile data are interpolated into 1 m depth bins for all variables; data are provided for every profile.

Beschreibung: Discrete measurements of particulate organic carbon (POC) concentration and flux were made on the RRS Discovery during COMICS cruise DY086 at site P3 in the South Atlantic from November to December, 2017 (Giering et al. 2023). Data is from a variety of equipment including marine snow catchers, neutrally-buoyant sediment traps (PELAGRA) and a stand-alone pump system. Marine snow catchers settled on-deck for 2 hours. Slow sinking particles were collected from the base and fast sinking particles were collected from the tray. These data were used along with bottle POC data to calibrate glider backscatter data from the GOCART project.

Beschreibung: The future response of marine ecosystem diversity to continued anthropogenic forcing is poorly constrained. Phytoplankton are a diverse set of organisms that form the base of the marine ecosystem. Currently, ocean biogeochemistry and ecosystem models used for climate change projections typically include only 2−3 phytoplankton types and are, therefore, too simple to adequately assess the potential for changes in plankton community structure. Here, we analyse a complex ecosystem model with 35 phytoplankton types to evaluate the changes in phytoplankton community composition, turnover and size structure over the 21st century. We find that the rate of turnover in the phytoplankton community becomes faster during this century, that is, the community structure becomes increasingly unstable in response to climate change. Combined with alterations to phytoplankton diversity, our results imply a loss of ecological resilience with likely knock-on effects on the productivity and functioning of the marine environment.