Metadata Report for BODC Series Reference Number 541717

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

PROVESS Northern North Sea (NNS) Site SeaSoar Deployments

Northern North Sea Site (59° 20.0' N, 1° 00.0' E)

The SeaSoar was deployed by RVS (Research Vessels Services, Southampton Oceanographic Centre, UK) for J. Howarth of CCMS Proudman Oceanographic Laboratory, UK during PROVESS cruise Pelagia PE125 at the Northern North Sea site. The deployment took place in the vicinity of the mooring site and consisted of three box surveys:

• Survey 1 (SS1) from 21/10/1998 18:57 to 22/10/1998 07:57 (12 hrs) extended between 59.3081 and 59.5831 °N and between 0.5002 and 1.4319 °E.
• Survey 2 (SS2) from 23/10/1998 19:53 to 24/10/1998 07:48 (12 hrs) extended between 59.0832 and 59.3084 °N, and between 0.6663 and 1.3319 °E.
• Survey 3 (SS3) from 27/10/1998 13:35 to 28/10/1998 07:04 (16 hrs) extended between 59.1552 and 59.4995° N, and between 0.6666 and 1.3336 °E. This last survey also included a diagonal section within the box.

Most of the time the SeaSoar was on 200 metres of tow cable giving a depth range of approx. 80 metres. Surveys were carried out at an average speed of 6 to 8 knots.

RVS/SOC SeaSoar

SeaSoar Instrument Description

The SeaSoar is a hydrodynamic fish towed behind the ship travelling at 8-9 knots linked by a faired cable. The usual cable length is 800m, which allows the fish to oscillate between the surface and a depth of 500m.

The unit has two stub wings whose angle of attack may be set by hydraulic servo motors. Thus the fish is able to climb or dive under the control of command signals from the ship or, more usually, by automatic command signals driven by the on-board pressure sensor. The wavelength and amplitude of the locus of the fish through the water depend upon the cable length, the ship's speed and the angle of attack selected for the wings.

The fish can carry a range of sensors. Invariably, a CTD is fitted but fluorometers, transmissometers, light sensors and plankton counters may also be included.

The instrument was developed by the Institute of Oceanographic Sciences, Wormley (now Southampton Oceanographic Centre) and was subsequently made available commercially.

Pelagia PE125 SeaSoar Data Processing Documentation

Instrumentation and Sampling

The SeaSoar was equipped with a Neil Brown MkIII CTD fitted with a Chelsea Instrument MkIII fluorometer. Bottle water samples were collected for salinity (Dave Teare, RVS) and chlorophyll (K. Wild-Allen, NUE) analyses. The samples were drawn from the ship Aqua-flow system at the beginning and end of survey and at approx. 4 hours interval during each survey when the SeaSoar was at approx. 4 metres depth (also the depth of the Aqua-flow intake). These samples were used for the calibration of the different instruments. Although an oxygen sensor was also fitted on the SeaSoar, the data were not included in the final data series because no oxygen calibration samples were taken during the cruise.

Data Acquisition and On Board Processing

The data were logged by a Research Vessel Services Level 'A' microcomputer that dynamically reduced the sampling frequency to 1Hz and applied a time stamp from PC internal clock. There was then a failure during the cruise to process the data further. As a result, the reduced data were logged on the Level 'C' (a Sun workstation) at the Southampton Oceanographic Laboratory after the cruise.

Initial calibrations were applied to convert the raw counts into engineering units. The times associated with the SeaSoar data were then corrected by taking into account the start time for recording as logged to the PC file and the offset of the PC internal clock to the ship's master clock logged on the ABC system. The time uncertainty associated with this correction is not in excess of 20 seconds.

BODC Calibrations

Pressure

The accuracy of the pressure channel was examined by considering the pressure values when the SeaSoar was logging in the air (as indicated by salinity values <1 PSU). Pressure readings in air (888 datapoints for Survey 1, 478 for Survey 2 and 1806 for Survey 3) were sufficiently close to zero (ranging from -0.09 to +0.39 db) and no correction was applied to the pressure channel.

Salinity

Salinity was calibrated using water samples collected from the ship's non- toxic seawater supply when the SeaSoar was close to the surface. The samples were analysed on a Guildline Autosal bench salinometer calibrated against OSI standard seawater. A significant offset was observed for the three surveys and the following corrections were applied to the data:

SS1: calibrated salinity = SeaSoar Sal + 0.043 PSU (SD= +/-0.016, n=5)
SS2: calibrated salinity = SeaSoar Sal + 0.043 PSU (SD= +/-0.012, n=4)
SS3: calibrated salinity = SeaSoar Sal + 0.014 PSU (SD= +/-0.002, n=3)

The calibrated SeaSoar data from the depth range of 3-6 decibars were then compared with corresponding calibrated salinity data from the surface underway thermosalinograph record in order to check for instrument drift. No significant drift was detected for any of the three surveys.

Temperature

Temperature was checked by comparing SeaSoar data from the depth range 3-6 decibars with corresponding calibrated temperature data from the surface underway thermosalinograph record. The difference between the two data sets was not significant and consequently the SeaSoar temperature data were left unchanged.

Chlorophyll

For the calibration of the SeaSoar fluorescence channel, variations in surface distribution were too small to derive a significant calibration equation from surface data only. Extracted chlorophyll values from samples taken from the non-toxic supply during the SeaSoar surveys were therefore combined with extracted chlorophyll measured on samples taken at different depths during the CTD stations just prior and after each survey. These were compared with SeaSoar fluorometer voltages from the first two profiles of each SeaSoar survey averaged within ±1 db of the samples' depth.

The resulting calibration equation applied to the data was as follow:

Chl (mg Chl m^-3) = exp (3.66 Voltages - 4.99) (R² =0.93, n=22)

BODC Data Processing

Navigation was added to the calibrated SeaSoar data by matching the time channels from the SeaSoar data and the ABC navigation file.

The calibrated data were screened using the BODC SERPLO interactive graphical editor. All suspect data were flagged by setting the quality control byte to 'M'.

The limits of the individual profiles contained in the data set were marked by setting the pressure channel flag to 'B' and 'E' to signify 'beginning' and 'end' respectively.

The data series were 'topped and tailed' to eliminate corrupt data collected during deployment and recovery of the fish.

Project Information

PROcesses of Vertical Exchange in Shelf Seas (PROVESS)

Introduction

PROVESS was an interdisciplinary study of the vertical fluxes of properties through the water column and the surface and bottom boundary layers. The project was funded by the European Community MAST-III programme (MAS3-CT97- 0159) and ran from March 1998 to May 2001.

Scientific Rationale

PROVESS was based on the integration of experimental, theoretical and modelling studies with the aim of improving understanding and quantification of vertical exchange processes in the water column, in particular in the surface and benthic boundary layers and across the> pycnocline. PROVESS also explored mechanisms of physical-biological coupling in which vertical exchanges and turbulence significantly affect the environmental conditions experienced by the biota with particular reference to aggregation, flocculation, sedimentation and trophic interactions.

Fieldwork

The experimental phase of the project was carried out at two contrasting sites in the North Sea: the northern North Sea site (NNS) and the southern North Sea site (SNS).

The two sites had the following characteristics:

At both locations measurements were concentrated at a central position with additional measurements being made to estimate horizontal gradients. Moored instruments (including current meters, temperature and pressure sensors, fluorometers, transmissometers, nutrient analysers and meteorological sensors) were deployed between 7 September and 5 November 1998 at the NNS and between 29 March and 25 May 1999 at the SNS. Each experiment was supported by intensive measurement series made from oceanographic ships and involving turbulence dissipation profiler CTD, particle size profilers, optical profilers, benthic sampling and water bottle sampling.

Details of the cruises were as follows:

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: