Metadata Report for BODC Series Reference Number 686172

• 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

RD Instruments- Ocean Surveyor 75kHz Vessel mounted ADCP.

¹ Ranges at 1 to 5 knots ship speed are typical and vary with situation.
² Single-ping standard deviation.
³ User's choice of depth cell size is not limited to the typical values specified.

Profile Parameters

• Velocity long-term accuracy (typical): ±1.0%, ±0.5cm/s
• Velocity range: -5 to 9m/s
• # of depth cells: 1 - 128
• Max ping rate: 0.7

Bottom Track

Maximum altitude (precision <2cm/s): 950m

Echo Intensity Profile

Dynamic range: 80dB
Precision: ±1.5dB

Transducer and Hardware

Beam angle: 30°
Configuration: 4-beam phased array
Communications: RS-232 or RS-422 hex-ASCII or binary output at 1200 - 115,200 baud
Output power: 1000W

Standard Sensors

Temperature (mounted on transducer)

• Range: -5° to 45°C
• Precision: ±0.1°C
• Resolution: 0.03°

Environmental

Operating temperature: -5° to 40°C (-5° to 45°C)*
Storage temperature: -30° to 50°C (-30° to 60°C)*

*later instruments have greater range.

Web Page

Further details can be found on the manufacturer's website or in the specification sheet

RRS Discovery 286 75kHz VMADCP

Deployment and originator's processing

Two RDI Vessel-Mounted Acoustic Doppler Current Profilers (VM-ADCPs) were operated on Discovery 286; the 150kHz VM-ADCP and the 75 kHz Phased Array instrument (Ocean Surveyor) that had been fitted immediately prior to FISHES (Discovery 253, May-June 2001). The 150 kHz ADCP is mounted in the hull 1.75 m to port of the keel, 33 m aft of the bow at the waterline and at an approximate depth of 5 m. The 75 kHz ADCP is mounted in a second well in the hull, but 4.15 m forward and 2.5 m to starboard of the 150 kHz well. The instrument was configured to sample over 120 second intervals with 60 bins of 16m depth, pulse length 16m and a blank beyond transmit of 8m. The instrument is a narrow band phased array ADCP with 76.8 kHz frequency and a 30° beam angle. The PC was running RDI software VmDAS v1.3. Gyro heading, and GPS Ashtech heading, location and time were fed as NMEA messages into the software which was configured to use the Gyro heading for co-ordinate transformation. The software logs the PC clock time, stamps the data (start of each ensemble) with that time, and records the offset of the PC clock from GPS time. This offset was applied to the data in the processing path before merging with navigation. The ADCP was fitted in the forward well as previously noted. It was known to have a heading alignment offset of 60°, this offset was not accounted for in the RDI software configuration. Bottom tracking was switched on early in the cruise and at the end of the first leg for calibration purposes.

In parallel with the 150 KHz ADCP, a calibration of the 75 kHz ADCP was achieved using bottom tracking data available from our departure across the Agulhas Bank. Using long, straight, steady speed sections of standard two minute ensemble profiles (.STA files) we obtained a calibration of tanØ=-1.7508 (±s.d.= 0.0244),Ø= 60.26° and A =1.0018 (±s.d.= 0.0060)

BODC processing

A total of 35 files were submitted to BODC. The data were supplied in P* binary format. The table below lists the variables transferred into the BODC internal format (a subset of NetCDF and BODC's format for 2 dimensionsal datacycle storage). Variables not transferred were the non-calibrated backscatter channels.

Screening and Data quality

The data have been visually screened for obvious problems using the BODC EDSERPLO software. No significant problems were detected.

Project Information

CROZet natural iron bloom EXport experiment (CROZEX)

The multidisciplinary CROZet natural iron bloom EXport experiment (CROZEX) was a major component of the Natural Environment Research Council (NERC) funded core strategic project Biophysical Interactions and Controls over Export Production (BICEP). The project is the first planned natural iron fertilisation experiment to have been conducted in the Southern Ocean.

The overall objective of CROZEX was to examine, from surface to sediment, the structure, causes and consequences of a naturally occurring phytoplankton bloom in the Southern Ocean. The Crozet Plateau was chosen as the study area. This area typically exhibits two phytoplankton blooms a year, a primary bloom in that peaks in October and a secondary bloom in December or January. Specific aims with respect to these were to:

• Determine what limits the primary bloom
• Determine the cause of the secondary bloom

The project was run by the George Deacon Division (GDD), now Ocean Biogeochemistry and Ecosystems (OBE) at the National Oceanography Centre Southampton (NOCS). Participants from five other university departments also contributed to the project.

The project ran from November 2004 to January 2008 with marine data collection between 3^rd November 2004 and 21^st January 2005. There were 2 cruises to the Crozet Islands Plateau, which are summarised in Table 1.

Table 1: Details of the RRS Discovery CROZEX cruises.

The two cruises aimed to survey two areas at different phases of the bloom cycle described above. A control area to the south of the Crozet Islands, which is classified as High Nutrient Low Chorophyll (HNLC), where the blooms do not occur and a second area in the region of the blooms to the north of the Crozet Islands.

Sampling was undertaken at ten major stations (see Pollard et al., 2007) numbered M1 to M10. The following observations/sampling were conducted at each station where possible:

• Several CTD casts sampling:
  • Iron (using a titanium rig)
  • ²³⁴Th
  • Physical parameters (temperature, salinity etc)
  • Oxygen
  • CO₂
  • Nutrients using a stainless steel rig including a Lowered Acoustic Doppler Current Profiller (LADCP)
• At each thorium cast there was an associated Stand Alone Pump System (SAPS) deployment
• At some stations, a drifting PELAGRA trap was deployed for the duration of the work
• Megacoring was undertaken at M5 and M6
• Gravity coring was undertaken at M5, M6 and M10
• Longhurst Hardy Plankton Recorder (LPHR) tows were undertaken at a few major stations

For each of the major stations (M1 to M10), the following were determined:

• Primary productivity
• New Production
• Phytoplankton community composition
• Bacterial activity
• Iron
• Nutrient drawdown
• Thorium export

Sampling between major stations included:

• SeaSoar runs instrumented with:
  • CTD
  • Optical Plankton Counter (OPC)
  • Fast Repetition Rate fluorimeter (FRRf)
• Physics CTD casts on several lines
• Argo float deployments
• Zooplankton nets at nearly every CTD and major station
• Underway and on-station CO₂ measurements
• Underway nutrients and radium sampling
• 5 to 6 day ship-board iron-addition incubation experiments
• Checks against near-real-time satellite and model data
• Mooring deployments based on the satellite imagery in support of the CROZET (Benthic CROZEX) project.

The CROZEX cruises included 6 extra days in support of the CROZET (Benthic CROZEX) project, whose main cruise took place one year after the CROZEX cruises. The CROZET work undertaken during the CROZEX cruises was primarily the moored sediment trap deployments, although some of the coring work is applicable to both projects.

CROZEX produced significant findings in several disciplines, including confirmation that iron from Crozet fertilised the bloom and that phytoplankton production rates and most export flux estimates were much larger in the bloom area than the HNLC area (Pollard et al. 2007). Many of the project results are presented in a special CROZEX issue of Deep-Sea Research II (volume 54, 2007).

References

Pollard R., Sanders R., Lucas M. and Statham P., 2007. The Crozet natural iron bloom and export experiment (CROZEX). Deep-Sea Research II, 54, 1905-1914.

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: