NERC North Sea Project Data Set (1988-1990)

The North Sea Project evolved from a review by the Natural Environment Research Council (NERC) of shelf seas research, which identified the need for a concerted multidisciplinary study of circulation, transport and production. The Project was adopted by NERC as their first Community Research Project to run from 1987 to 1992. The ultimate aim of the North Sea Project was the development of a suite of prognostic water quality models to aid management of the North Sea. Data management for the Project was carried out by BODC. To ensure sufficient resolution of the seasonal cycle 15 cruises each lasting 12 days and following the same 1800 nautical mile track, were repeated monthly by RRS Challenger.

The CTD profiles from the stations and underway sampling at 30 second intervals (a total of 500,000 data cycles) provided three dimensional distributions of conductivity (for salinity), temperature, depth, dissolved oxygen, transmittance (for suspended sediment concentration), fluorescence (for chlorophyll) and irradiance. Water bottle samples were collected on almost all CTD casts, usually with bottles being fired at the bottom, middle and top of a cast. Many different parameters were measured from these water samples. In order to calibrate the CTD sensors, temperatures were obtained from reversing thermometers and salinity determinations and dissolved oxygen measurements were made. Spectrophotometric chlorophyll and phaeopigment determinations were carried out, the chlorophyll values for a cruise were used to calibrate the CTD fluorometer. Sediment content was determined and the values used to calibrate the transmissometer.

Nutrients (nitrate, nitrite, silicate, phosphate and ammonium) were determined from water bottle samples using an autoanalyser. On eight of the survey cruises (between February and October 1989) measurements were made of dimethyl sulphide (DMS) and its cellular precursor, dimethyl sulphoniopropionate (DMSP). These determinations were carried out using gas chromatography. In addition to the DMS measurements, low molecular weight halocarbons have been determined. Dissolved and particulate trace metals (Mn, Cu, Pb, Zn, Cd, Co, Ni, Fe, Hg, As, Al) were measured on survey cruises during May 1988, August 1988, January 1989 and May 1989.

Primary productivity was investigated on each survey cruise, the uptake of Carbon-14 being measured in an on-deck incubator. Water bottle samples from a pre-dawn CTD cast were taken from six depths (usually 1, 3, 7, 15, 20 and 30m) instead of the more usual top, middle and bottom samples. Triplicate samples were then incubated at six simulated depths for a 24 hour period.

During the survey cruises a water sample was collected for microscopic analysis of phytoplankton numbers and species composition at every other CTD station. The area covered by the survey cruises was split into fifteen representative regions and one or two samples falling within each area analyzed for each survey cruise.

Zooplankton samples were taken at half the stations on all but one of the survey cruises by the Netherlands Institute for Sea Research. The air-sea interaction components of the North Sea survey comprised four experiments measuring organic particles, inorganic (trace metal) particles, large airborne particles and rainfall.

Benthic processes were investigated with sediment cores taken on eight survey cruises at six sites of varied character, three being in the area of summer stratification. Oxygen uptake and sulphate reduction rates were measured to investigate aerobic and anaerobic microbial activity; also fluxes and profiles of nutrients, sedimentary characteristics, organic matter, water content, particle size and temperature. The oxygen content in the overlying water was also measured.

Current profiles were recorded at 10 minute intervals (with 4m bin size) underway by the shipborne ADCP (Acoustic Doppler Current Profiler) on all survey cruises.

Six current meter stations were maintained over the fifteen month survey period. Instruments were recovered and redeployed on each of the survey cruises. Three of the moorings (B, E and F) were made up of Aanderaa and S4 current meters, while the other three (A, C and D) were bottom mounted ADCPs. In addition, at four sites (A, B, C and D), moored thermistor chains were deployed during the stratification season. Recording fluorometers were also deployed at sites A and E between February and May 1989. Data recovery from the moorings was about 80 per cent.

Alternating with the survey cruises were process study cruises which investigated some particular aspect of the science of the North Sea. The process cruises fell into six main categories although there was some overlap between the data collected and the processes studied. The process studies were as follows: fronts (nearshore, circulation and mixing), sandwaves and sandbanks, plume (Humber, Wash, Thames and Rhine), resuspension, air-sea exchange, productivity and blooms. For most process study cruises surface underway data, CTD casts and water bottle samples were taken, in the same way as on the survey cruises. However, although all the sensors for the survey cruises were available, not all were calibrated for the process study cruises. In addition, other more specialized data were collected relevant to the process being studied.

After the main data collection period (August 1988 - October 1989), a series of cruises took place between October 1989 and October 1990 which followed up the intensive data collection work. Process studies relating to blooms, plumes (Humber, Wash, Rhine), sandwaves and the flux of contaminants through the Dover Strait were carried out as well as two 'survey' cruises.

AVAILABILITY: Complete data set for 38 cruises published on CD-ROM (340 Mbytes), supporting software on floppy disk.

[This description was derived from the BODC WWW pages.]