Metadata Report for BODC Series Reference Number 1081367

• 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

Discovery Cruise D371 AMT21 CTD Data Quality Document

Temperature, salinity and sigma-theta: Entrainment features were visible in a number of casts, both in the frame mounted (primary) and vane mounted (secondary channels). These features were apparent throughout the thermocline/pycnocline and continued down to approximately 200 dbar. The level of entrainment can be indicated by a variation between data points of 0.2 °C in the temperature, of 0.03 in the salinity and 0.1 kg m^-3 in sigma-theta. Observations of the data indicated that the vane mounted sensors suffered less from entrainment than did the sensors in the frame (due to their position outside the water mass of the CTD frame structure) and therefore the secondary temperature, salinity and density were retained for banking in the NODB, while primary channels were discarded.

Chlorophyll: In circumstances where data were collected at pressures > 200 dbar, negative concentrations were frequently visible. These were flagged as anomalous. These resulted from the chlorophyll calibration being optimised for the euphotic zone, in particular the fluorescence/chlorophyll maximum. There were casts (CTD009, CTD020, CTD022, CTD029) with notable maxima above the Deep Chlorophyll Maximum (DCM) but no flags were applied to these profiles as no outliers could be identified.

Down and up-welling PAR irradiance: Optics casts were taken pre-dawn and at solar noon. Therefore, for almost half the casts, the PAR values are negligible as they were recorded in the dark. Participants on the cruise noted a number of occasions where the vessel was not held on station with the sun on the starboard side of the vessel (where the CTD and optics rigs were deployed) for the solar noon optics station. For these casts, the CTD frame had therefore to descend through the ship's shadow. In two instances (CTD022 and CTD024), this led to the downwelling irradiance values in the near-surface section of the profile (approximately the top 50 dbar) being flagged. The upwelling signal for these casts did not appear affected in the same way and was left un-flagged. There were a number of other profiles where there were near-surface variations in both the upwelling and downwelling channels. In these instances, it was judged that the variation was most likely due to changes in cloud cover and the casts (CTD014, CTD038, CTD040, CTD044, CTD047, CTD049, CTD056, CTD058, CTD060, CTD064) were left un-flagged.

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

Sea-Bird Dissolved Oxygen Sensor SBE 43 and SBE 43F

The SBE 43 is a dissolved oxygen sensor designed for marine applications. It incorporates a high-performance Clark polarographic membrane with a pump that continuously plumbs water through it, preventing algal growth and the development of anoxic conditions when the sensor is taking measurements.

Two configurations are available: SBE 43 produces a voltage output and can be incorporated with any Sea-Bird CTD that accepts input from a 0-5 volt auxiliary sensor, while the SBE 43F produces a frequency output and can be integrated with an SBE 52-MP (Moored Profiler CTD) or used for OEM applications. The specifications below are common to both.

Specifications

Further details can be found in the manufacturer's specification sheet.

Discovery Cruise D371 AMT21 CTD Instrumentation

The CTD unit was a Sea-Bird Electronics 911plus system, with dissolved oxygen sensor. The CTD was fitted with up and downwelling PAR sensors, a BBRTD, transmissometer and a fluorometer. All instruments were attached to a 24 position stainless steel Sea-Bird SBE 32 carousel (s/n 32-37898-0518). The table below lists more detailed information about the various sensors.

Change of sensors during cruise: The PAR sensors were removed for cast 51 as it was deeper than 1000 m. The backscatter sensor was replaced prior to cast 11. The underwater unit and pressure transducer were changed prior to cast 33.

Sampling device

Rosette sampling system equipped with 24 x 20 l sampling bottles (manufactured by Ocean Test Equipment Inc.).

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:

Further details can be found in the manufacturer's specification sheet.

Chelsea Technologies Group Aquatracka MKIII fluorometer

The Chelsea Technologies Group Aquatracka MKIII is a logarithmic response fluorometer. Filters are available to enable the instrument to measure chlorophyll, rhodamine, fluorescein and turbidity.

It uses a pulsed (5.5 Hz) xenon light source discharging along two signal paths to eliminate variations in the flashlamp intensity. The reference path measures the intensity of the light source whilst the signal path measures the intensity of the light emitted from the specimen under test. The reference signal and the emitted light signals are then applied to a ratiometric circuit. In this circuit, the ratio of returned signal to reference signal is computed and scaled logarithmically to achieve a wide dynamic range. The logarithmic conversion accuracy is maintained at better than one percent of the reading over the full output range of the instrument.

Two variants of the instrument are available, both manufactured in titanium, capable of operating in depths from shallow water down to 2000 m and 6000 m respectively. The optical characteristics of the instrument in its different detection modes are visible below:

* The wavelengths for the turbidity filters are customer selectable but must be in the range 400 to 700 nm. The same wavelength is used in the excitation path and the emission path.

The instrument measures chlorophyll a, rhodamine and fluorescein with a concentration range of 0.01 µg l^-1 to 100 µg l^-1. The concentration range for turbidity is 0.01 to 100 FTU (other wavelengths are available on request).

The instrument accuracy is ± 0.02 µg l^-1 (or ± 3% of the reading, whichever is greater) for chlorophyll a, rhodamine and fluorescein. The accuracy for turbidity, over a 0 - 10 FTU range, is ± 0.02 FTU (or ± 3% of the reading, whichever is greater).

Further details are available from the Aquatracka MKIII specification sheet.

Chelsea Technologies Photosynthetically Active Radiation (PAR) Irradiance Sensor

This sensor was originally designed to assist the study of marine photosynthesis. With the use of logarithmic amplication, the sensor covers a range of 6 orders of magnitude, which avoids setting up the sensor range for the expected signal level for different ambient conditions.

The sensor consists of a hollow PTFE 2-pi collector supported by a clear acetal dome diverting light to a filter and photodiode from which a cosine response is obtained. The sensor can be used in moorings, profiling or deployed in towed vehicles and can measure both upwelling and downwelling light.

Specifications

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:

Further details can be found in the manufacturer's specification sheet.

RRS Discovery Cruise D371 AMT21 CTD Processing

Sampling strategy

All casts were conventional profiling casts with water sampling. A stainless steel (SS) CTD system was used. The frame was normally deployed pre-dawn and at solar noon each day.

A total of 73 out of 74 CTD casts were completed during the cruise. Cast 66 was cancelled due to problems with the winch shortly after deployment.

BODC Cruise processing

CTD casts were recorded using the Sea-Bird data collection software Seasave-Win32. The software outputs were then processed following the BODC recommended guidelines using SBE Data Processing-Win32 v7.20g; the processing routines are named after each stage in brackets < >. The software applied the calibrations as appropriate through the instrument configuration file to the data in engineering units output by the CTD hardware.

An ascii file (CNV) containing the 24 Hz data for up and down casts was generated from the binary Sea-Bird files for each cast <DatCnv>. Files were created for each cast containing the mean values of all the variables at the bottle firing events <Bottle Summary>. Using the CNV files processing routines were applied to remove pressure spikes <WildEdit>, the oxygen sensor was then shifted relative to the pressure by 2 seconds, to compensate for the lag in the sensor response time <AlignCTD> and the effect of thermal 'inertia' on the conductivity cells was removed <CellTM>. The surface soak was identified for each cast, removed and LoopEdit run. Salinity and oxygen concentration were re-derived and density (sigma-T with channel 1 and sigma-theta with channel 2) were derived <Derive> after the corrections for sensor lag and thermal 'inertia' had been applied. The CTD files produced from Sea-Bird processing were converted from 24 Hz ascii files into 2 Hz ascii files of the complete cast (down and upcasts) with all channels for archive at BODC and also to 1 dbar downcast files for calibration and visualisation onboard <BinAverage>. The initial salinity and oxygen channels produced at the DatCnv stage, along with the conductivity, voltage and altimeter channels were removed from the 1 dbar downcast files <Strip>.

The Sea-Bird 1 dbar downcast files were converted from the Sea-Bird CNV format to the tab delimited ODV format using the mapping described below:

Calibrated salinity, oxygen and fluorometer channels were then added to the profiles using calibration equations derived from the bottle file data compared against discrete samples collected from the CTD water bottles on each cast.

Field Calibrations

• Pressure

  No adjustments were made to the values resulting from application of manufacturer's coefficients during the initial processing.

• Temperature

  Temperature readings from the two temperature sensors were almost identical outside of entrainment features and no other independent measurements of better quality were available. No further correction was therefore applied to the data.

• Salinity

  The salinity data were calibrated by comparing the sensor readings from the up-cast at the point when the bottles were fired with the discrete salinity data measured using the bench salinometer on water samples collected from fired bottles. The samples collected were from four depths for each cast. Offsets were generated between the salinometer and CTD sensor values and plotted against cast and salinometer values. The linear regressions from the offset against bench salinometer data were significant for both sensors (p < 0.0001).

  Calibration	N	R2
  Salinity_1_calibrated = 0.9986 (±0.0069) * Salinity_1_SBEcal + 0.0509 (±0.0002)	283	0.15
  Salinity_2_calibrated = 0.9989 (±0.0066) * Salinity_2_SBEcal + 0.0400 (±0.0001)	283	0.10

  The calibration reduction to the RMS residual (sensor 1: uncalibrated = 0.0032, calibrated = 0.0029; sensor 2: uncalibrated = 0.0033, calibrated = 0.0026) although small, indicated an improved match to the bench salinometer sample dataset after calibration.

• Dissolved oxygen

  The oxygen sensors were calibrated by comparing the SBE43 sensor readings from the CTD up-cast at the point when the bottles were fired with the dissolved oxygen concentrations from Winkler titrations on water samples collected from the fired bottles. The samples collected were from a range of depths on a number of casts throughout the cruise. The linear regressions from the offset (Winkler titration data - SBE43 data) against Winkler titration data was significant (p < 0.0001).

  Calibration (in ml l-1)	N	R2
  Oxygen_cal_ml = 1.0287 (±0.0026) * Oxygen_conc_ml + 0.0874 (±0.0126)	286	0.29

  The reduction in the RMS residual (uncalibrated = 0.257, calibrated = 0.135) indicated an improved match to the Winkler titration dataset after calibration.

• Fluorescence

  The CTD deployed Chelsea AQUAtracka MkIII fluorometer was calibrated against extracted chlorophyll-a measurements made on seawater collected by Niskin bottles on each cast. Samples of seawater from CTD niskin bottles were collected to calibrate the CTD fluorometer with the analytical method following Welschmeyer (1994). Samples were collected at 73 stations from an average of 9 depths including light depths from 97, 55, 33, 14, 7, 1 and 0.1%. Each sample of 250 ml was filtered through 47 mm 0.2 µm polycarbonate filters. The filters were then placed in a vial with 10 ml 90% acetone and left in a freezer for 24 hours. The samples were then analysed on a pre-calibrated Turner Designs Trilogy fluorometer with a non-acidified chl module (CHL NA #046) fitted. The calibration was checked against dilutions of pure chlorophyll stock during the cruise and no modifications to the calibration were necessary.

  The Chelsea AQUAtracka MkIII fluorometer attached to the CTD rig operated without problem. The sample calibrations were applied on a cast by cast basis.

  References

  Welschmeyer N.A., 1994. Fluorometric analysis of chlorophyll-a in the presence of chlorophyll-b and phaeopigments. Limnology and Oceanography, 39(8), 1985-1992.

  Cast	Calibration (in mg m-3)	N	R2
  1	Fluo_calibrated = 3.019 * Fluo_notional - 0.027	7	0.995
  2	Fluo_calibrated = 2.618 * Fluo_notional - 0.034	7	0.993
  3	Fluo_calibrated = 1.190 * Fluo_notional + 0.014	8	0.675
  4	Fluo_calibrated = 1.499 * Fluo_notional + 0.007	7	0.734
  5	Fluo_calibrated = 1.758 * Fluo_notional + 0.008	8	0.972
  6	Fluo_calibrated = 1.418 * Fluo_notional + 0.022	7	0.827
  7	Fluo_calibrated = 1.950 * Fluo_notional + 0.060	8	0.989
  8	Fluo_calibrated = 2.189 * Fluo_notional + 0.049	8	0.965
  9	Fluo_calibrated = 1.866 * Fluo_notional + 0.021	9	0.930
  10	Fluo_calibrated = 2.068 * Fluo_notional + 0.052	8	0.932
  11	Fluo_calibrated = 2.385 * Fluo_notional + 0.064	9	0.948
  12	Fluo_calibrated = 3.320 * Fluo_notional + 0.038	10	0.968
  13	Fluo_calibrated = 4.002 * Fluo_notional - 0.006	10	0.994
  14	Fluo_calibrated = 3.613 * Fluo_notional + 0.020	10	0.975
  15	Fluo_calibrated = 3.069 * Fluo_notional + 0.055	8	0.977
  16	Fluo_calibrated = 7.082 * Fluo_notional + 0.045	6	0.980
  17	Fluo_calibrated = 3.536 * Fluo_notional + 0.009	9	0.994
  18	Fluo_calibrated = 5.744 * Fluo_notional - 0.039	8	0.987
  19	Fluo_calibrated = 5.277 * Fluo_notional - 0.014	8	0.990
  20	Fluo_calibrated = 4.948 * Fluo_notional + 0.003	8	0.993
  21	Fluo_calibrated = 4.699 * Fluo_notional - 0.018	9	0.999
  22	Fluo_calibrated = 6.925 * Fluo_notional - 0.092	8	0.997
  23	Fluo_calibrated = 6.382 * Fluo_notional - 0.086	6	0.999
  24	Fluo_calibrated = 5.917 * Fluo_notional + 0.049	9	1.000
  25	Fluo_calibrated = 4.843 * Fluo_notional - 0.045	8	0.979
  26	Fluo_calibrated = 6.583 * Fluo_notional - 0.106	10	0.994
  27	Fluo_calibrated = 3.902 * Fluo_notional + 0.004	7	0.969
  28	Fluo_calibrated = 4.850 * Fluo_notional - 0.019	9	0.995
  29	Fluo_calibrated = 4.562 * Fluo_notional - 0.014	9	0.998
  30	Fluo_calibrated = 4.773 * Fluo_notional - 0.031	10	0.996
  31	Fluo_calibrated = 5.562 * Fluo_notional + 0.004	8	0.996
  32	Fluo_calibrated = 5.945 * Fluo_notional - 0.014	9	0.995
  33	Fluo_calibrated = 7.994 * Fluo_notional - 0.058	9	0.997
  34	Fluo_calibrated = 4.941 * Fluo_notional + 0.055	9	0.991
  35	Fluo_calibrated = 5.612 * Fluo_notional - 0.024	9	0.993
  36	Fluo_calibrated = 5.498 * Fluo_notional + 0.021	9	0.995
  37	Fluo_calibrated = 8.124 * Fluo_notional - 0.093	9	1.000
  38	Fluo_calibrated = 7.645 * Fluo_notional - 0.046	9	1.000
  39	Fluo_calibrated = 7.457 * Fluo_notional - 0.045	9	0.998
  40	Fluo_calibrated = 4.883 * Fluo_notional + 0.054	9	0.994
  41	Fluo_calibrated = 5.269 * Fluo_notional - 0.066	9	0.998
  42	Fluo_calibrated = 2.901 * Fluo_notional + 0.110	9	0.983
  43	Fluo_calibrated = 3.146 * Fluo_notional - 0.070	6	0.977
  44	Fluo_calibrated = 4.579 * Fluo_notional - 0.008	9	0.994
  45	Fluo_calibrated = 3.532 * Fluo_notional + 0.057	8	0.991
  46	Fluo_calibrated = 4.170 * Fluo_notional - 0.013	9	0.995
  47	Fluo_calibrated = 5.136 * Fluo_notional - 0.006	9	0.994
  48	Fluo_calibrated = 6.540 * Fluo_notional - 0.034	9	0.996
  49	Fluo_calibrated = 4.055 * Fluo_notional + 0.046	8	0.991
  50	Fluo_calibrated = 3.690 * Fluo_notional + 0.026	8	0.982
  51	Fluo_calibrated = 3.726 * Fluo_notional + 0.033	9	0.981
  52	Fluo_calibrated = 5.869 * Fluo_notional - 0.040	9	0.993
  53	Fluo_calibrated = 5.949 * Fluo_notional - 0.051	9	0.994
  54	Fluo_calibrated = 6.506 * Fluo_notional - 0.069	9	0.994
  55	Fluo_calibrated = 7.576 * Fluo_notional - 0.104	9	0.999
  56	Fluo_calibrated = 5.984 * Fluo_notional - 0.021	9	0.997
  57	Fluo_calibrated = 4.344 * Fluo_notional - 0.004	9	0.997
  58	Fluo_calibrated = 4.207 * Fluo_notional + 0.040	9	0.997
  59	Fluo_calibrated = 3.928 * Fluo_notional + 0.014	9	0.998
  60	Fluo_calibrated = 2.891 * Fluo_notional + 0.044	9	0.988
  61	Fluo_calibrated = 2.782 * Fluo_notional + 0.053	9	0.986
  62	Fluo_calibrated = 3.421 * Fluo_notional + 0.011	9	0.992
  63	Fluo_calibrated = 2.461 * Fluo_notional + 0.066	9	0.995
  64	Fluo_calibrated = 3.994 * Fluo_notional + 0.070	9	0.968
  65	Fluo_calibrated = 4.080 * Fluo_notional + 0.008	9	0.997
  67	Fluo_calibrated = 2.316 * Fluo_notional + 0.005	9	0.984
  68	Fluo_calibrated = 2.503 * Fluo_notional + 0.071	8	0.954
  69	Fluo_calibrated = 1.369 * Fluo_notional + 0.008	9	0.739
  70	Fluo_calibrated = 1.563 * Fluo_notional + 0.072	9	0.707
  71	Fluo_calibrated = 1.566 * Fluo_notional + 0.046	9	0.828
  72	Fluo_calibrated = 2.077 * Fluo_notional + 0.139	8	0.792
  73	Fluo_calibrated = 1.806 * Fluo_notional + 0.021	9	0.910
  74	Fluo_calibrated = 1.785 * Fluo_notional + 0.079	9	0.867

  The reduction in the RMS residual (uncalibrated = 0.329, calibrated = 0.090) over the entire cruise indicated an improved match to the extracted chl-a sample dataset after calibration.

BODC post-processing and screening

• Reformatting

  The data were converted from tab delimited ODV format into BODC internal format using BODC transfer function 401. Only the final calibrated channels were transferred and the following table shows how these variables were mapped to appropriate BODC parameter codes. Oxygen saturation and sigma-theta were derived and added to the profiles during the transfer.

  Originator's Parameter Name	Units	Description	BODC Parameter Code	Units	Comments
  Pressure	dbar	Pressure of the water column	PRESPR01	dbar	-
  Temperature_1	°C	Temperature of water column by CTD	TEMPST01	°C	Frame mounted sensor
  Temperature_2	°C	Temperature of water column by CTD	TEMPST02	°C	Vane mounted sensor
  Salinity_1_calibrated	-	Practical salinity of the water body by CTD	PSALCC01	-	Frame mounted sensor. Calibration against bench salinometer samples
  Salinity_2_calibrated	-	Practical salinity of the water body by CTD	PSALCC02	-	Vane mounted sensor. Calibration against bench salinometer samples
  Oxy_cal_ml	ml l-1	Oxygen	DOXYSC01	µmol l-1	Calibration against Winkler samples. Unit conversion *44.66 applied.
  Fluo_calibrated	mg m-3	Chlorophyll-a	CPHLPS01	mg m-3	Calibration against extracted chl-a samples
  PAR_down	W m-2	Downwelling PAR irradiance	DWIRPP01	W m-2	No data for cast 51.
  PAR_up	W m-2	Upwelling PAR irradiance	UWIRPP01	W m-2	No data for cast 51.
  -	-	Oxygen saturation	OXYSSC01	%	Generated by BODC using the Benson and Krause (1984) algorithm with parameters DOXYSC01, PSALCC01 and TEMPST01
  -	-	Sigma-theta	SIGTPR01	kg m-3	Generated by BODC using the Fofonoff and Millard (1982) algorithm from frame mounted sensors.
  -	-	Sigma-theta	SIGTPR02	kg m-3	Generated by BODC using the Fofonoff and Millard (1982) algorithm from vane mounted sensors.

• References

  Benson, B.B. and Krause, D., 1984. The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere. Limnology and Oceanography, 29(3), 620-632.

  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.

• Screening

  Reformatted CTD data were transferred onto a graphics work station for visualisation using the in-house editor EDSERPLO. No data values were edited or deleted. Flagging was achieved by modification of the associated BODC quality control flag for suspect or null values.

  The vane mounted sensors suffered less from entrainment that did the sensors in the frame and therefore the secondary temperature, salinity and density were retained for banking in the NODB, while the primary channels were discarded.

Banking

The profiles were banked to the National Oceanographic Database (NODB) following BODC procedures.

Project Information

Oceans 2025 Theme 10, Sustained Observation Activity 1: The Atlantic Meridional Transect (AMT)

The Atlantic Meridional Transect has been operational since 1995 and through the Oceans 2025 programme secures funding for a further five cruises during the period 2007-2012. The AMT programme began in 1995 utilising the passage of the RRS James Clark Ross between the UK and the Falkland Islands southwards in September and northwards in April each year. Prior to Oceans 2025 the AMT programme has completed 18 cruises following this transect in the Atlantic Ocean. This sustained observing system aims to provide basin-scale understanding of the distribution of planktonic communities, their nutrient turnover and biogenic export in the context of hydrographic and biogeochemical provinces of the North and South Atlantic Oceans.

The Atlantic Meridional Transect Programme is an open ocean in situ observing system that will:

• give early warning of any fundamental change in Atlantic ecosystem functionng
• improve forecasts of the future ocean state and associated socio-economic impacts
• provide a "contextual" logistical and scientific infrastructure for independently-funded national and international open ocean biogeochemical and ecological research.

The specific objectives are:

• To collect hydrographic, chemical, ecological and optical data on transects between the UK and the Falkland Islands
• To quantify the nature and causes of ecological and biogeochemical variability in planktonic ecosystems
• To assess the effects of variability in planktonic ecosystems on biogenic export and on air-sea exchange of radiatively active gases

The measurements taken and experiments carried out on the AMT cruises will be closely linked to Themes 2 and 5. The planned cruise track also allows for the AMT data to be used in providing spatial context to the Sustained Observation Activities at the Porcupine Abyssal Plain Ocean Observatory (SO2) and the Western Channel Observatory (SO10).

More detailed information on this Work Package is available at pages 6 - 9 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10

Weblink: http://www.oceans2025.org/

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: