Metadata Report for BODC Series Reference Number 1028897

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

Data Description

Data Category

Currents -subsurface Eulerian

Instrument Type

Name	Categories
Teledyne RDI Ocean Surveyor 75 kHz vessel-mounted ADCP	current profilers

Instrument Mounting

research vessel

Originating Country

United Kingdom

Originator

Dr Brian King

Originating Organization

National Oceanography Centre, Southampton

Processing Status

banked

Online delivery of data

Download not available

Project(s)

Oceans 2025
Oceans 2025 Theme 1 WP1.2
Oceans 2025 Theme 10 SO3: MOC

Data Identifiers

Originator's Identifier	OS75_DI346NNX_01
BODC Series Reference	1028897

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm)	2010-01-06 07:39
End Time (yyyy-mm-dd hh:mm)	2010-02-18 10:34
Nominal Cycle Interval	150.0 seconds

Spatial Co-ordinates

Start Latitude	26.64140 N ( 26° 38.5' N )
End Latitude	37.93230 N ( 37° 55.9' N )
Start Longitude	79.07980 W ( 79° 4.8' W )
End Longitude	9.34440 W ( 9° 20.7' W )
Positional Uncertainty	0.0 to 0.01 n.miles
Minimum Sensor or Sampling Depth	29.23 m
Maximum Sensor or Sampling Depth	1053.3 m
Minimum Sensor or Sampling Height	-
Maximum Sensor or Sampling Height	-
Sea Floor Depth	-
Sea Floor Depth Source	-
Sensor or Sampling Distribution	Sensor fixed with measurements made at multiple depths within a fixed range (e.g. ADCP) - The sensor is at a fixed depth, but measurements are made remotely from the sensor over a range of depths (e.g. ADCP measurements)
Sensor or Sampling Depth Datum	Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum	-

Parameters

BODC CODE	Rank	Units	Title
BINNUMBR	0	Dimensionless	Bin number
AADYAA01	1	Days	Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01	1	Days	Time (time between 00:00 UT and timestamp)
ACYCAA01	1	Dimensionless	Sequence number
ALATGP01	1	Degrees	Latitude north relative to WGS84 by unspecified GPS system
ALONGP01	1	Degrees	Longitude east relative to WGS84 by unspecified GPS system
APEWGP01	1	Centimetres per second	Eastward velocity of measurement platform relative to ground surface by unspecified GPS system
APNSGP01	1	Centimetres per second	Northward velocity of measurement platform relative to ground surface by unspecified GPS system
DBINAA01	2	Metres	Depth (spatial coordinate) of ADCP bin relative to water surface {bin depth} in the water body
LCEWAS01	2	Centimetres per second	Eastward velocity of water current (Eulerian measurement) in the water body by shipborne acoustic doppler current profiler (ADCP)
LCNSAS01	2	Centimetres per second	Northward velocity of water current (Eulerian measurement) in the water body by shipborne acoustic doppler current profiler (ADCP)

Definition of Rank
Rank 1 is a one-dimensional parameter Rank 2 is a two-dimensional parameter Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No Problem Report Found in the Database

Data Quality

During processing, the data originator noted the following issues with data quality:

Bubbles

Bubbles being present immediately below the transducer face can present a problem for ADCP data. There were few instances of bubbles creating problems during the cruise, apart from on 20 January 2010, when it is thought that the high velocities observed were spurious and caused by bubbles.

Anomalous Scattering Bias

A more extensive issue was the presence of anomalous scattering layers, created by light scattering particles such as zooplankton, leading to along-track velocity bias. On this cruise a large anomalous scattering layer was found between 460 and 660 metres across much of the section. The affected bins were not removed as this would also have removed good data.

Navigation

It was noticed that the navigation information had dropped out due to a splitter box problem. When this problem was fixed it was realised that the navigation data were not being fed to the VmDas system. The problem had begun at 23:15 28 January 2010. However, the data were logged in the TECHSAS system, so the navigation data were copied into the VMADCP data from the TECHSAS system.

On 28 January 2010, the navigation source was switched from the GPS4000 to the GPSG12 at approximately 23:20. However, the files after this period were found to again lack navigation data. This affected data from 23:20 28 January to 14:54 on 30 January, and once again the TECHSAS data were used to correct the navigation. At this point the navigation input was switched back to the GPS4000.

Data Access Policy

Open Data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

Narrative Documents

Instrument Description

A 75 kHz Teledyne RD Instruments Ocean Surveyor ADCP was fitted to the hull of the RSS Discovery, while docked in Freeport. The transducers were installed at a depth of 5.3 m.

The transducer is phased-array, which means that it is made up of many elements each transmitting in different phase. This is advantageous, because it means that the accuracy of the velocities, derived from the Doppler shifted signal is not affected by speed of sound changes throughout the water column.

The navigation data from the RRS Discovery GPS system was input into the VMADCP data; this was mainly from the Trimble 4000 GPS system. The blanking depth of the instrument was set to 8 m and the instrument was set to sample 60 bins, at 16 m depth per bin.

RD Instruments- Ocean Surveyor 75kHz Vessel mounted ADCP.

Long-Range Mode
Vertical Resolution Cell Size³	Max. Range (m)¹	Precision (cm/s)²
8m	520 - 650	30
16m	560 - 700	17
High-Precision Mode
Vertical Resolution Cell Size³	Max. Range (m)¹	Precision (cm/s)²
8m	310 - 430	12
16m	350 - 450	9

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

BODC Processing

The VMADCP data were provided to BODC as a single NetCDF file that covered a period from 07:39:35 on 06 January to 10:34:07 on 18 February 2010. This file was transferred to QXF format, which is a subset of NetCDF, using BODC generated Matlab code. It is BODC policy that ADCP data are reported from the middle of the ADCP depth bin. Using the formula:

Center of Bin = Transducer depth + Blank Depth + (Bin Depth/2)

it was found that the data provided were given to the bottom of the bin. BODC subtracted 8 from the depth to give the data at the middle of the bin.

During the transfer, the originator variables are mapped to BODC generated parameter codes and any variables that require unit conversion have the conversions applied. The parameter mapping and unit conversions can be seen in the table below.

Originator's variable	Units	Description	BODC Parameter Code	Units	Comments
lon	Degrees (0 - 360)	Longitude	ALONGP01	Degrees (-180 - +180)	Values converted by subtraction of 360
lat	Degrees (-108 - +180)	Latitude	ALATGP01	Degrees (-180 - +180)	-
depth (of bin)	m	Depth of middle of ADCP bin	DBINAA01	m	Values converted by subtraction of 8
uabs	cm s^-1	Absolute East-West current velocity	LCEWAS01	cm s^-1	Eastern values are positive
vabs	cm s^-1	Absolute North-South current velocity	LCNSAS01	cm s^-1	Northern values are positive
uship	m s^-1	Ship's East-West velocity	APEWGP01	cm s^-1	Values converted by multiplication by 100. Eastern values are positive
vship	m s^-1	Ship's North-South velocity	APNSGP01	cm s^-1	Values converted by multiplication by 100. Northern values are positive
speed	cm s^-1	Scalar current speed	-	-	Variable not transferred. Superseded by vector values
shipspd	cm s^-1	Scalar ship speed	-	-	Variable not transferred. Superseded by vector values

Following transfer the data were screened using BODC in-house visualisation software. Any suspect data points were flagged with the appropriate BODC quality control flag.

Originator's Data Processing

The RRS Discovery cruise D346 took place between 05 January and 19 February 2010 and formed part of the RAPID-MOC project. Prior to the cruise a 75 kHz vessel-mounted Acoustic Doppler Current Profiler (ADCP) was fitted to the hull of the ship. The data from the instrument were acquired using RD Instruments VmDas software package version 1.42.

The instrument was run in narrowband single-ping mode and for the first few days, up to 09 January, it was run in bottom track mode to obtain an accurate phase and amplitude calibration. Typically, the instrument was switched between bottom tracking and water tracking close to 900 m. The final processing of the data was performed using the Common Ocean Data Access System (CODAS) provided by the University of Hawaii.

Calibration

The best calibration estimates are obtained when the velocity data is collected using the sea bed as a reference point. However, this is only possible when the sea bed is within range of the instrument. The ADCP was run in bottom tracking mode from 06 to 09 January and again when RRS Discovery reached the Moroccan continental shelf, in order to verify that the rotations had not altered during the section. The following calibration was applied to the data during bottom tracking mode.

Rotation angle = -2.88

Rotation amplitude = 1.002

The following calibration was applied to the data during water tracking mode.

Rotation angle = -2.1194

Rotation amplitude = 1.0015

The numbers are slightly different, but this is to be expected as it is difficult for the ship to maintain a fixed position while on station, due to a lack of dynamic propulsion. The calibrations were applied to the data before the data were inspected using the Gautoedit package within CODAS.

Project Information

Oceans 2025 - The NERC Marine Centres' Strategic Research Programme 2007-2012

Who funds the programme?

The Natural Environment Research Council (NERC) funds the Oceans 2025 programme, which was originally planned in the context of NERC's 2002-2007 strategy and later realigned to NERC's subsequent strategy (Next Generation Science for Planet Earth; NERC 2007).

Who is involved in the programme?

The Oceans 2025 programme was designed by and is to be implemented through seven leading UK marine centres. The marine centres work together in coordination and are also supported by cooperation and input from government bodies, universities and other partners. The seven marine centres are:

National Oceanography Centre, Southampton (NOCS)
Plymouth Marine Laboratory (PML)
Marine Biological Association (MBA)
Sir Alister Hardy Foundation for Marine Science (SAHFOS)
Proudman Oceanographic Laboratory (POL)
Scottish Association for Marine Science (SAMS)
Sea Mammal Research Unit (SMRU)

Oceans2025 provides funding to three national marine facilities, which provide services to the wider UK marine community, in addition to the Oceans 2025 community. These facilities are:

British Oceanographic Data Centre (BODC), hosted at POL
Permanent Service for Mean Sea Level (PSMSL), hosted at POL
Culture Collection of Algae and Protozoa (CCAP), hosted at SAMS

The NERC-run Strategic Ocean Funding Initiative (SOFI) provides additional support to the programme by funding additional research projects and studentships that closely complement the Oceans 2025 programme, primarily through universities.

What is the programme about?

Oceans 2025 sets out to address some key challenges that face the UK as a result of a changing marine environment. The research funded through the programme sets out to increase understanding of the size, nature and impacts of these changes, with the aim to:

improve knowledge of how the seas behave, not just now but in the future;
help assess what that might mean for the Earth system and for society;
assist in developing sustainable solutions for the management of marine resources for future generations;
enhance the research capabilities and facilities available for UK marine science.

In order to address these aims there are nine science themes supported by the Oceans 2025 programme:

Climate, circulation and sea level (Theme 1)
Marine biogeochemical cycles (Theme 2)
Shelf and coastal processes (Theme 3)
Biodiversity and ecosystem functioning (Theme 4)
Continental margins and deep ocean (Theme 5)
Sustainable marine resources (Theme 6)
Technology development (Theme 8)
Next generation ocean prediction (Theme 9)
Integration of sustained observations in the marine environment (Theme 10)

In the original programme proposal there was a theme on health and human impacts (Theme 7). The elements of this Theme have subsequently been included in Themes 3 and 9.

When is the programme active?

The programme started in April 2007 with funding for 5 years.

Brief summary of the programme fieldwork/data

Programme fieldwork and data collection are to be achieved through:

physical, biological and chemical parameters sampling throughout the North and South Atlantic during collaborative research cruises aboard NERC's research vessels RRS Discovery, RRS James Cook and RRS James Clark Ross;
the Continuous Plankton Recorder being deployed by SAHFOS in the North Atlantic and North Pacific on 'ships of opportunity';
physical parameters measured and relayed in near real-time by fixed moorings and ARGO floats;
coastal and shelf sea observatory data (Liverpool Bay Coastal Observatory (LBCO) and Western Channel Observatory (WCO)) using the RV Prince Madog and RV Quest.

The data is to be fed into models for validation and future projections. Greater detail can be found in the Theme documents.

Oceans 2025 Theme 1, Work Package 1.2: Atlantic Circulation and Transports

This Work Package is run by the National Oceanography Centre, Southampton (NOCS) and aims to establish whether the Atlantic Meridional Overturning Circulation (MOC) is slowing down, and to relate this to changes in regional storage of heat, freshwater and carbon.

More detailed information on this Work Package is available at pages 8 - 10 of the official Oceans 2025 Theme 1 document: Oceans 2025 Theme 1

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

Oceans 2025 Theme 10, Sustained Observation Activity 3: Monitoring the Atlantic Meridional Overturning Circulation

The Meridional Overturning Circulation (MOC) is the key component of ocean circulation in the Atlantic responding to climate change. Under the NERC directed programme Rapid Climate Change (RAPID) two arrays of instruments have been positioned in the ocean to monitor the MOC, one at 26.5 °N to capture the southward flow at depth, and the Western Atlantic Variability Experiment (WAVE) array across the Canadian-US continental slope, closer to the presumed source variations. Sustained Observation Activity (SO) 3 will continue these measurements to observe the strength and structure of the MOC, working closely with Oceans 2025 Theme 1 and the RAPID-WATCH directed programme.

There are two elements to this SO activity. SO 3.1. relates to the E-W mooring array in the mid-North Atlantic at 26.5 °N while SO 3.2. is concerned with the Western Atlantic array between Cape Cod and the Grand Banks.

Aims and Purpose of SO 3.1.

The purpose of the observing system is to measure and understand the current state and variability of the MOC. The results will help assess the risks of rapid climate change from a slow down in the MOC, by providing the necessary data for coupled climate models to predict future climate. This work will be carried out by the National Oceanography Centre, Southampton (NOCS).

Aims and Purpose of SO 3.2.

The overall aim is to maintain and service the WAVE monitoring array, to measure changes in the North Atlantic thermohaline circulation along the western boundary of the North Atlantic. This array complements the NOC 26.5 °N meridional section by providing information from north of the Gulf Stream, closer to the presumed source of variations in MOC. This work will be supported by the Proudman Oceanographic Laboratory (POL).

More detailed information on this Work Package is available at pages 11 - 14 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10

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

Data Activity or Cruise Information

Cruise

Cruise Name	D346
Departure Date	2010-01-05
Arrival Date	2010-02-19
Principal Scientist(s)	Brian A King (National Oceanography Centre, Southampton)
Ship	RRS Discovery

Complete Cruise Metadata Report is available here

Fixed Station Information

Station Name	24.5 degrees N Hydrographic Transatlantic section - A05
Category	Offshore route/traverse

24.5 degrees N Hydrographic Transatlantic section - A05

The hydrographic transatlantic section at 24.5 degrees North has been occupied 8 times, namely in 1957, 1981, 1992, 1998, 2004, 2010, 2015 and 2020. The section is an attempt to calculate the transports of water and its constituents (heat, salinity, nutrients, biological productivity) along this latitude, and to compare the data so that the degree of change in the North Atlantic transports can be revealed. The Hydrographic Programme of the international World Ocean Circulation Experiment (WOCE) designated this section as A05. Since WOCE, the section occupations contribute to the Global Ocean Ship-Based Hydrographic Investigations Program (GO-SHIP).

Map of stations

BODC image

The station positions for most of the occupied sections are shown in the above figures. Sections occupied in 1957, 1981, 1992, 1998 and 2004 are shown in the upper figure. The section occupied in 2010 is shown in the lower figure.

The 1957 and 1992 sections each went zonally along 24.5 degrees N from the African coast to the Bahama Islands. Because of diplomatic clearance issues, the 1981, 1998, 2004, 2010 and 2015 sections angled southwestward from the African coast at about 28 degrees N to join the 24.5 degrees N section at about 23 degrees W. The 1998, 2004 and 2010 sections angled northwestward at about 73 degrees W to finish the section along 26.5 degrees N. The 2010 and 2020 sections deviated from the previous sections across the Mid-Atlantic Ridge (MAR) in order to sample the deepest channel and capture the passage of the deep water across the MAR.

Table 1: Occupations of the section

Year	Cruise	Reference
1957	-	Fuglister (1960)
1981	-	Roemmich and Wunsch (1985)
1992	RV Hesperides HE06	Parilla et al. (1994)
1998	RV Ronald H. Brown	Baringer and Molinari (1999)
2004	RRS Discovery D279	Bryden et al. (2005b)
2010	RRS Discovery D346	King et al. (2012)
2015	RRS Discovery DY040	King et al. (2016)
2020	RRS James Cook JC191	Sanchez-Franks, A. (2020)

References

Baringer, M. O. N. and R. L. Molinari, 1999. Atlantic Ocean baroclinic heat flux at 24 to 26°N. Geophysical Research Letters, 26, 353-356.

Bryden, H. L., H. R. Longworth, and S. Cunningham, 2005b. Slowing of the Atlantic meridional overturning circulation at 25°N. Nature, 438, 655-657.

Fuglister, F. C., 1960. Atlantic Ocean Atlas of Temperature and Salinity Profiles and Data from the International Geophysical Year of 1957-1958. Vol. 1, Woods Hole Oceanographic Institution Atlas Series, WHOI, Woods Hole, Massachusetts.

King, B. A. et al., 2012. RRS Discovery Cruise 346, 05 Jan-19 Feb 2010. The 2010 transatlantic hydrography section at 24.5N. Southampton, UK, National Oceanography Centre Southampton, 177pp. (National Oceanography Centre Cruise Report, No. 16).

King, B. A. et al., 2016. RRS Discovery Cruise DY040 (RAGNARoCC), 06 Dec 2015 - 22 Jan 2016. The 2015 transatlantic hydrography section at 24.5N. Southampton, UK, National Oceanography Centre Southampton, 159pp. (National Oceanography Centre Cruise Report).

Parilla, G., A.Lavin, H. Bryden, M. Garcia, and R. Millard, 1994. Rising temperatures in the subtropical North Atlantic Ocean over the past 35 years. Nature, 369, 48-51.

Roemmich, D. and C. Wunsch, 1985. Two transatlantic sections: meridional circulation and heat flux in the subtropical North Atlantic Ocean. Deep Sea Research, 32, 619-664.

Sanchez-Franks, A., 2020. RRS James Cook Cruise JC191, 19 January - 1 March 2020. Hydrographic sections from the Florida Straits to the Canaries Current across 24N in the Atlantic Ocean. Southampton, UK, National Oceanography Centre Southampton, 262pp. (National Oceanography Centre Cruise Report, No. 70).

Related Fixed Station activities are detailed in Appendix 1

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

SeaDataNet Quality Control Flags