Metadata Report for BODC Series Reference Number 1088723
Metadata Summary
Problem Reports
Data Access Policy
Data Policy
Narrative Documents
Project Information
Data Activity or Cruise Information
Fixed Station Information
BODC Quality Flags
Metadata Summary
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Problem Reports
No Problem Report Found in the Database
Data Access Policy
DIMES Programme Data Access Conditions - phase 1
The data are currently under the following restriction:
- The data are restricted to use solely by the Principal Investigator (PI) and project co-workers.
Data Policy
DIMES Data Policy
Data management arrangements for the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) consortium programme (NERC Reference: NE/E006663/1) are expected to:
- Encourage dissemination of scientific results
- Protect the rights of the individual scientists
- Treat all the involved researchers equitably
- Ensure the quality of the data in the NOCS data archive
Data collected within NERC funded research at NOC will comply with NERC's policy on data management. The main objective of this policy is to ensure that the data will contribute to a key NERC resource. Data will continue to be exploited both scientifically and commercially long after the formal end of the programme. The management of the data collected during NOC research will be the responsibility of the relevant NERC Designated Data Centres (e.g. BODC).
Data access policy
The following data policy framework applies to DIMES. It is subject to lead investigator or steering committee overview. The data policy will apply to all research grants, studentships and contracts funded through DIMES.
- Data1 should be lodged with the BODC, together with such metadata as are defined by BODC (see http://www.bodc.ac.uk/data/data_submission/), ideally within six months of acquisition2
- 2. Data will be made immediately available by the BODC to the DIMES community, then publicly available after three years3. Exceptions are made for Climate Variability and Predictability (CLIVAR) and studentship related data (see below).
- 3. In the case of PhD students supported by DIMES, data central to the student's study will not generally be released by the BODC for the duration of the studentship. This is nominally four years from acquisition after which the data will become publicly available. Extension to the embargo period must be agreed between the Data Centre, the DIMES Science Coordinator and the student's supervisor. These rules do not imply that the student has exclusive rights to DIMES data.
- In the case of data destined for public access data assembly centers, e.g. CLIVAR, these will be not be embargoed and will be made publicly available from both the data assembly centre and BODC.
- Any corrections, improvements or amendments to data must be lodged with the data centre as soon as possible.
- PIs making use of project data are responsible for ensuring that the data used in publications are the best available at the time.
- During the time when data are restricted from the public domain, no data will be transferred to parties outside the project without the explicit agreement of the originator. In addition, guidance will need to be sought from the project Principal Investigator, Science Coordinator or Steering Committee if major data transfers are involved. This avoids compromising the interests of other project participants.
- In the event of dispute, the final decision rests with the project Princaipal Investigator, Science Coordinator or Steering Committee.
- PIs and/or co-workers failing to comply with the data policy would be subject to appropriate sanctions.
- 1 Data must be final version i.e. calibrated, quality controlled and in a state ready for use by other researchers. It is not sufficient to supply raw or partially processed data that may be superseded.
- 2 Acquisition for data generated on a cruise the date of the end of the cruise. For moorings acquisition is the date of recovery and for post cruise sample analysis acquisition is the date of the processing.
- 3 3 year restriction period is relative to the date of acquisition.
Narrative Documents
Instrument Descriptions
CTD Unit and Auxiliary Sensors
| Sensor | Model | Serial Number | Calibration (UT) | Comments |
|---|---|---|---|---|
| CTD underwater unit | Sea-Bird 9plus underwater unit | 09P-54047-0943 | - | - |
| Submersible pump | Sea-Bird 5T submersible pump | 05T-3607 | - | - |
| Secondary submersible pump | Sea-Bird 5T submersible pump | 05T-3195 | - | - |
| Carousel 24 position pylon | Sea-Bird 32 Carousel 24 position pylon | 32-19817-0243 | - | Equipped with 24 Niskin sampling bottles |
| CTD deck unit | Sea-Bird 11plus deck unit | 11P-34173-0676 | - | - |
| Pressure transducer | Digiquartz temperature compensated pressure sensor | 110557 | 26/04/2009 | - |
| Conductivity sensor | Sea-Bird 4C conductivity sensor | 04C-3054 | 10/08/2011 | - |
| Temperature sensor | Sea-Bird 3P temperature sensor | 03P-4151 | 1/09/2010 | - |
| Secondary temperature sensor | Sea-Bird 3P temperature sensor | 03P-2919 | - | - |
| Secondary conductivity sensor | Sea-Bird 4C conductivity sensor | 04C-3580 | - | - |
| Dissolved oxygen sensor | Sea-Bird 43 dissolved oxygen sensor | 43-0363 | - | - |
| Fluorometer | Chelsea MKIII Aquatracka fluorometer | 88-2615-124 | - | - |
| Altimeter | Benthos PSA-916T altimeter | 41302 | - | - |
| Turbidity sensor | User Supplied turbidity sensor | - | - | - |
| Light scattering sensor | WETLabs light scattering sensor | BBRTD-759R | - | - |
| Transmissometer | Chelsea MKII 10 cm path Alphatracka transmissometer | 161050 | - | - |
Sea-Bird Electronics SBE 911 and SBE 917 series CTD profilers
The SBE 911 and SBE 917 series of conductivity-temperature-depth (CTD) units are used to collect hydrographic profiles, including temperature, conductivity and pressure as standard. Each profiler consists of an underwater unit and deck unit or SEARAM. Auxiliary sensors, such as fluorometers, dissolved oxygen sensors and transmissometers, and carousel water samplers are commonly added to the underwater unit.
Underwater unit
The CTD underwater unit (SBE 9 or SBE 9 plus) comprises a protective cage (usually with a carousel water sampler), including a main pressure housing containing power supplies, acquisition electronics, telemetry circuitry, and a suite of modular sensors. The original SBE 9 incorporated Sea-Bird's standard modular SBE 3 temperature sensor and SBE 4 conductivity sensor, and a Paroscientific Digiquartz pressure sensor. The conductivity cell was connected to a pump-fed plastic tubing circuit that could include auxiliary sensors. Each SBE 9 unit was custom built to individual specification. The SBE 9 was replaced in 1997 by an off-the-shelf version, termed the SBE 9 plus, that incorporated the SBE 3 plus (or SBE 3P) temperature sensor, SBE 4C conductivity sensor and a Paroscientific Digiquartz pressure sensor. Sensors could be connected to a pump-fed plastic tubing circuit or stand-alone.
Temperature, conductivity and pressure sensors
The conductivity, temperature, and pressure sensors supplied with Sea-Bird CTD systems have outputs in the form of variable frequencies, which are measured using high-speed parallel counters. The resulting count totals are converted to numeric representations of the original frequencies, which bear a direct relationship to temperature, conductivity or pressure. Sampling frequencies for these sensors are typically set at 24 Hz.
The temperature sensing element is a glass-coated thermistor bead, pressure-protected inside a stainless steel tube, while the conductivity sensing element is a cylindrical, flow-through, borosilicate glass cell with three internal platinum electrodes. Thermistor resistance or conductivity cell resistance, respectively, is the controlling element in an optimized Wien Bridge oscillator circuit, which produces a frequency output that can be converted to a temperature or conductivity reading. These sensors are available with depth ratings of 6800 m (aluminium housing) or 10500 m (titanium housing). The Paroscientific Digiquartz pressure sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.
Additional sensors
Optional sensors for dissolved oxygen, pH, light transmission, fluorescence and others do not require the very high levels of resolution needed in the primary CTD channels, nor do these sensors generally offer variable frequency outputs. Accordingly, signals from the auxiliary sensors are acquired using a conventional voltage-input multiplexed A/D converter (optional). Some Sea-Bird CTDs use a strain gauge pressure sensor (Senso-Metrics) in which case their pressure output data is in the same form as that from the auxiliary sensors as described above.
Deck unit or SEARAM
Each underwater unit is connected to a power supply and data logging system: the SBE 11 (or SBE 11 plus) deck unit allows real-time interfacing between the deck and the underwater unit via a conductive wire, while the submersible SBE 17 (or SBE 17 plus) SEARAM plugs directly into the underwater unit and data are downloaded on recovery of the CTD. The combination of SBE 9 and SBE 17 or SBE 11 are termed SBE 917 or SBE 911, respectively, while the combinations of SBE 9 plus and SBE 17 plus or SBE 11 plus are termed SBE 917 plus or SBE 911 plus.
Specifications
Specifications for the SBE 9 plus underwater unit are listed below:
| Parameter | Range | Initial accuracy | Resolution at 24 Hz | Response time |
|---|---|---|---|---|
| Temperature | -5 to 35°C | 0.001°C | 0.0002°C | 0.065 sec |
| Conductivity | 0 to 7 S m-1 | 0.0003 S m-1 | 0.00004 S m-1 | 0.065 sec (pumped) |
| Pressure | 0 to full scale (1400, 2000, 4200, 6800 or 10500 m) | 0.015% of full scale | 0.001% of full scale | 0.015 sec |
Further details can be found in the manufacturer's specification sheet.
Paroscientific Absolute Pressure Transducers Series 3000 and 4000
Paroscientific Series 3000 and 4000 pressure transducers use a Digiquartz pressure sensor to provide high accuracy and precision data. The sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.
The 3000 series of transducers includes one model, the 31K-101, whereas the 4000 series includes several models, listed in the table below. All transducers exhibit repeatability of better than ±0.01% full pressure scale, hysteresis of better than ±0.02% full scale and acceleration sensitivity of ±0.008% full scale /g (three axis average). Pressure resolution is better than 0.0001% and accuracy is typically 0.01% over a broad range of temperatures.
Differences between the models lie in their pressure and operating temperature ranges, as detailed below:
| Model | Max. pressure (psia) | Max. pressure (MPa) | Temperature range (°C) |
|---|---|---|---|
| 31K-101 | 1000 | 6.9 | -54 to 107 |
| 42K-101 | 2000 | 13.8 | 0 to 125 |
| 43K-101 | 3000 | 20.7 | 0 to 125 |
| 46K-101 | 6000 | 41.4 | 0 to 125 |
| 410K-101 | 10000 | 68.9 | 0 to 125 |
| 415K-101 | 15000 | 103 | 0 to 50 |
| 420K-101 | 20000 | 138 | 0 to 50 |
| 430K-101 | 30000 | 207 | 0 to 50 |
| 440K-101 | 40000 | 276 | 0 to 50 |
Further details can be found in the manufacturer's specification sheet.
BODC Processing
The primary data (conductivity, temperature salinity) were received in a structured matlab format and converted into BODC internal format. The auxiliary sensor data will be processed separately. Potential temperature of the water body was derived by computation using UNESCO 1983 algorithm, σθ was derived by computation from salinity and potential temperature also using UNESCO 1983 algorithm. The following table shows how the variables within the matlab file were mapped to appropriate BODC parameter codes:
| Originator's Parameter Name | Units | Description | BODC Parameter Code | Units | Comments |
|---|---|---|---|---|---|
| temp | °C | Temperature from primary sensor | TEMPS901 | °C | - |
| sal | - | Practical salinity | PSALCC01 | Dimensionless | Calibrated against CTD bottle salinity samples |
| pres | dbar | Pressure exerted by the water column | PRESPR01 | dbar | - |
| - | - | Potential temperature | POTMCV01 | °C | Generated by BODC using the Fofonoff and Millard (1983) algorithm |
| - | - | σθ of the water column | SIGTPR01 | kg/m3 | Generated by BODC using the Fofonoff and Millard (1983) algorithm |
The reformatted data were visualised using the in-house EDSERPLO software. The data were screened and quality control flags were applied to data as necessary. Overall there were no quality issues and very few flags were added.
References
Fofonoff, N.P. and Millard, R.C., 1983. Algorithms for computations of fundamental properties of seawater. UNESCO Technical Papers in Marine Science, No.44, 53pp.
Originator's Data Processing
Sampling Strategy
Fifty five CTD profiles were performed during the cruise. The launch and recovery of the CTDs was done relatively slowly, especially in bad weather, due to the nature of the winch system on the ship. There was also a delay of a few minutes whilst the winch system was switched from box control to lab control at approximately 100 m of wire out. In addition, at stations where Vertical Microstructure Profilers (VMPs) were deployed, the CTD deployment duration had to approximately match the VMP cast duration, within 1.5 hours. There were several problems which occurred during the deployment of the CTDs. CTD007 was aborted due to early weight release of the VMP, CTD035 was delayed due bad weather and was made shallow (1875 m) due to VMP time constraint, CTD027 had a shallow bottom, CTD045 was aborted due to problem with the hydroboom, CTD054 was stopped due to bad weather, and during CTD048, the Sea-Bird software crashed and had to be restarted.
Data processing
The files were produced by Seasave and initial data processing was performed using Sea-Bird processing software. Firstly, the raw data were converted into physical units using 'DatCnv', the surface soak was removed from the data and the surface pressure offset obtained from the first 30 readings was applied. Temporal shifts were then applied to align the sensor readings using 'AlignCTD'. Corrections for the thermal mass of the cell were made using 'CellTM' and the output from the 'AlignCTD', in order to minimise salinity spiking in steep vertical gradients due to temperature/conductivity mismatch.
After the Sea-Bird processing, further processing was undertaken using the National Oceanography Centre's Mstar software package. Firstly, the data were averaged to 1 Hz, then the practical salinity and potential temperature were calculated. The downcast data were extracted, gaps were interpolated and the data were then averaged to 2 dbar. All profiles were visually checked to detect any possible anomalies, and profiles were also plotted on top of each other in order to detect any possible sensor drift. A number of small localised spikes were detected in the conductivity/salinity profiles and these were removed and replaced by null values.
Further details of the originator's processing can be found in the cruise report.
Field Calibrations
Salinity
Between five and seven Niskin bottles were sampled for salinity at each station. Surface and bottom Niskin bottles were chosen as well as a couple of bottles at tracer cluster depths (DIMES project released an inert chemical tracer at the upstream edge of the study area in late 2009). The differences i n salinity between the bottle salinities and the sensor salinities were found to be relatively scattered, but most differences were within ± 0.002. No clear trend or pattern in pressure or time dependence was identified, and both sensors showed similar behaviour. θ-S profiles were used to detect possible sensor drift, and all θ-S characteristics of bottom water sampled during the cruise were found to fall within the same narrow band. There was a change noted in the salinity from the beginning to end of the cruise, with fresher salinities at the beginning, however, this was thought to be a real change as it did not appear to be a constant shift and the difference was also consistent with previous bottom water studies. Based upon the analyses conducted, it was concluded that further calibration of the salinity data was not required, as the calibration applied would be less than the target accuracy.
Project Information
Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) project document
DIMES is a US/UK field program aimed at measuring diapycnal and isopycnal mixing in the Southern Ocean, along the tilting isopycnals of the Antarctic Circumpolar Current.
The Meridional Overturning Circulation (MOC) of the ocean is a critical regulator of the Earth's climate processes. Climate models are highly sensitive to the representation of mixing processes in the southern limb of the MOC, within the Southern Ocean, although the lack of extensive in situ observations of Southern Ocean mixing processes has made evaluation of mixing somewhat difficult. Theories and models of the Southern Ocean circulation have been built on the premise of adiabatic flow in the ocean interior, with diabatic processes confined to the upper-ocean mixed layer. Interior diapycnal mixing has often been assumed to be small, but a few recent studies have suggested that diapycnal mixing might be large in some locations, particularly over rough bathymetry. Depending on its extent, this interior diapycnal mixing could significantly affect the overall energetics and property balances for the Southern Ocean and in turn for the global ocean. The goals of DIMES are to obtain measurements that will help us quantify both along-isopycnal eddy-driven mixing and cross-isopycnal interior mixing.
DIMES includes tracer release, isopycnal following RAFOS floats, microstructure measurements, shearmeter floats, EM-APEX floats, a mooring array in Drake Passage, hydrographic observations, inverse modeling, and analysis of altimetry and numerical model output.
DIMES is sponsored by the National Science Foundation (U.S.), Natural Environment Research Council (U.K) and British Antarctic Survey (U.K.)
For more information please see the official project website at DIMES
Data Activity or Cruise Information
Cruise
| Cruise Name | JC054 |
| Departure Date | 2010-11-30 |
| Arrival Date | 2011-01-08 |
| Principal Scientist(s) | Mike Meredith (British Antarctic Survey) |
| Ship | RRS James Cook |
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:
| Flag | Description |
|---|---|
| Blank | Unqualified |
| < | Below detection limit |
| > | In excess of quoted value |
| A | Taxonomic flag for affinis (aff.) |
| B | Beginning of CTD Down/Up Cast |
| C | Taxonomic flag for confer (cf.) |
| D | Thermometric depth |
| E | End of CTD Down/Up Cast |
| G | Non-taxonomic biological characteristic uncertainty |
| H | Extrapolated value |
| I | Taxonomic flag for single species (sp.) |
| K | Improbable value - unknown quality control source |
| L | Improbable value - originator's quality control |
| M | Improbable value - BODC quality control |
| N | Null value |
| O | Improbable value - user quality control |
| P | Trace/calm |
| Q | Indeterminate |
| R | Replacement value |
| S | Estimated value |
| T | Interpolated value |
| U | Uncalibrated |
| W | Control value |
| X | Excessive difference |
