Metadata Report for BODC Series Reference Number 507587

• 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

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.

Challenger Cruise CH123A SeaSoar Data Processing

Instrumentation

The SeaSoar for this cruise was fitted with a Neil Brown MkIIIB CTD and a Chelsea Instruments Aquatracka fluorometer. Although the CTD unit included a Beckmann dissolved oxygen sensor the data have not been included in the final data set as no calibration samples were taken.

Data Acquisition

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 the ship's master clock. The reduced data were logged on the Level 'C' (a Sun workstation) via the Level 'B' disk buffer. Initial calibrations were applied to convert the raw counts into engineering units.

Calibration

Pressure

Further processing of the data was undertaken at BODC. Pressure was calibrated by considering the mean pressure logged in air (detected by salinity values <1 PSU). The following corrections were applied:

Series BSR507587 +1.9 decibars
Series BSR507599 +2.4 decibars
Series BSR507606 +2.1 decibars

Temperature

Temperature was checked by comparing SeaSoar data from the depth range 3-6 decibars with calibrated, contemporaneous thermosalinograph data. There was no significant difference between the two data sets and consequently the SeaSoar temperature data were left unchanged.

Salinity

Salinity was calibrated using three water samples collected from the ship's non-toxic seawater supply to coincide with the fish reaching the surface. The samples were analysed on a Guildline Autosal bench salinometer calibrated against OSI standard seawater. A correction of +0.015 PSU was applied to the data. The calibrated SeaSoar data from the depth range of 3- 6 decibars were compared with calibrated, contemporaneous thermosalinograph data to check for instrument drift. No significant drift was detected.

Chlorophyll

The underway fluorometer malfunctioned on this cruise. Consequently, the only calibration data that were available were four fluorometric extracted chlorophyll values taken from the non-toxic seawater supply. These were sampled over a voltage range from 1.26 to 1.35 volts whereas the good SeaSoar fluorometer data spanned the range 0.23 to 1.81 volts. Using the four calibration points available gave a very unusual calibration with a slope over 11 (1-3 is what one would expect). When applied to the SeaSoar data this gave the totally ridiculous answer of 63 mg/m3 for the maximum SeaSoar chlorophyll.

To overcome this problem, an extra 'calibration' data point was added. This was based on the assumption that the highest extracted chlorophyll value from the entire cruise was responsible for the highest SeaSoar fluorometer voltage. This assumption may be defended for a cruise working in a limited geographic area (the SES box) at a time of relatively low biological activity (November).

This produced a modified calibration of:

Chl = exp (V*2.18 - 4.53) (R2=68%, n=5)

Adopting this calibration reduced the maximum chlorophyll measured by SeaSoar to 0.55 mg/m3. The calibration has been applied to the data. Note that this 'calibration' will cause the SeaSoar to underestimate chlorophyll if the assumption used to derive the extra calibration point is invalid.

Data Processing

Navigation was added to the calibrated SeaSoar data by matching on time. Both data sets were logged using a common clock. Consequently, timing errors were not a problem. The navigation data were logged with a sampling interval of 30 seconds. Consequently, only one SeaSoar data point in thirty could be matched to a position. The remaining positions were determined by linear interpolation.

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

LOIS Shelf Edge Study (LOIS - SES)

Introduction

SES was a component of the NERC Land Ocean Interaction Study (LOIS) Community Research Programme that made intensive measurements from the shelf break in the region known as the Hebridean Slope from March 1995 to September 1996.

Scientific Rationale

SES was devoted to the study of interactions between the shelf seas and the open ocean. The specific objectives of the project were:

• To identify the time and space scales of ocean-shelf momentum transmission and to quantify the contributions to ocean-shelf water exchange by physical processes.

• To estimate fluxes of water, heat and certain dissolved and suspended constituents across a section of the shelf edge with special emphasis on net carbon export from, and nutrient import to, the shelf.

• To incorporate process understanding into models and test these models by comparison with observations and provide a basis for estimation of fluxes integrated over time and the length of the shelf.

Fieldwork

The SES fieldwork was focussed on a box enclosing two sections across the shelf break at 56.4-56.5 °N and 56.6-56.7 °N. Moored instrument arrays were maintained throughout the experiment at stations with water depths ranging from 140 m to 1500 m, although there were heavy losses due to the intensive fishing activity in the area. The moorings included meteorological buoys, current meters, transmissometers, fluorometers, nutrient analysers (but these never returned any usable data), thermistor chains, colour sensors and sediment traps.

The moorings were serviced by research cruises at approximately three-monthly intervals. In addition to the mooring work this cruises undertook intensive CTD, water bottle and benthic surveys with cruise durations of up to 6 weeks (3 legs of approximately 2 weeks each).

Moored instrument activities associated with SES comprised current measurements in the North Channel in 1993 and the Tiree Passage from 1995-1996. These provided boundary conditions for SES modelling activities.

Additional data were provided through cruises undertaken by the Defence Evaluation and Research Agency (DERA) in a co-operative programme known as SESAME.

Land Ocean Interaction Study (LOIS)

Introduction

The Land Ocean Interaction Study (LOIS) was a Community Research Project of the Natural Environment Research Council (NERC). The broad aim of LOIS was to gain an understanding of, and an ability to predict, the nature of environmental change in the coastal zone around the UK through an integrated study from the river catchments through to the shelf break.

LOIS was a collaborative, multidisciplinary study undertaken by scientists from NERC research laboratories and Higher Education institutions. The LOIS project was managed from NERC's Plymouth Marine Laboratory.

The project ran for six years from April 1992 until April 1998 with a further modelling and synthesis phase beginning in April 1998 and ending in April 2000.

Project Structure

LOIS consisted of the following components:

• River-Atmosphere-Coast Study (RACS)
  • RACS(A) - Atmospheric sub-component
  • RACS(C) - Coasts sub-component
  • RACS(R) - Rivers sub-component
  • BIOTA - Terrestrial salt marsh study
• Land Ocean Evolution Perspective Study (LOEPS)
• Shelf-Edge Study (SES)
• North Sea Modelling Study (NORMS)
• Data Management (DATA)

Marine Fieldwork

Marine field data were collected between September 1993 and September 1997 as part of RACS(C) and SES. The RACS data were collected throughout this period from the estuaries and coastal waters of the UK North Sea coast from Great Yarmouth to the Tweed. The SES data were collected between March 1995 and September 1996 from the Hebridean slope. Both the RACS and SES data sets incorporate a broad spectrum of measurements collected using moored instruments and research vessel surveys.

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: