Metadata Report for BODC Series Reference Number 2203763

• 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

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

Teledyne RDI's Workhorse Monitor ADCP

The Workhorse Monitor acoustic doppler current profler (Teledyne RD Instruments) is a long-range and long-term self contained ADCP. It has a patented four beam signal (300, 600 or 1200 kHz) and a standard depth rating of 200m or 600m. It operates effectively between temperatures of -5°C and 45°C and has a velocity accuracy of ±1% ±5mm/s.

CLASS Cruise JC191 CTD instrument description

CTD unit and auxiliary sensors

The CTD system used on cruise JC191 was a NOC 24-way stainless steel frame system consisting of a Sea-Bird 911 plus, with a Sea-Bird 32 carousel. The CTD frame was equipped with 20L Niskin bottles from cast 1 and a mixture of 10L and 20L Niskin bottles from cast 31. In addition the CTD was fitted with a number of scientific sensors as detailed in the table below. During the cruise various problems with sensors required them to be replaced on the CTD frame (see Section 1 of the JC191 cruise report). The table below shows which sensors were attached to the CTD frame and on which casts.

The cruise report states that the Altimeter was swapped from Cast 91 onwards however the data files contain the information for the Altimeter which was on Casts 1-92.

BODC Processing Lowered Acoustic Doppler Current Profiler (LADCP) from Cruise JC191

The LADCP data were supplied to BODC as 126 netCDF files and were converted to the BODC internal format. The following table shows how the variables within the files were mapped to appropriate BODC parameter codes:

All reformatted data were visualised using in-house Edserplo software and screened for suspect and missing data.

Please note that where data cycles for LCEWLW01 and LCNSLW01 were both null at the start and end of the data files, those cycles have been deleted from the files. Therefore the cycle channel numbering might not begin from 1. Any null cycles for LCEWLW01 and LCNSLW01 within the rest of the data files have been flagged as null (BODC flag N) but not deleted.

Additional data held at BODC

In addition to the above, the originators data files also included the variables listed below. These data have not been transferred into BODC internal format or undergone quality control.

For further information regarding any of the variables listed below please contact BODC.

Originator's Processing Lowered Acoustic Doppler Current Profiler (LADCP) from Cruise JC191

Sampling Strategy

A total of 126 LADCP stations were completed during JC191. Two self-logging Teledyne RDI Workhorse 300kHz Monitor lowered acoustic Doppler current profilers (LADCP) were installed onto the stainless steel CTD frame in a master/slave configuration, one in a downward-looking (master) position and the other in an upward-looking (slave) position. Both LADCP's were powered by an NMF Workhorse battery pack. Before each cast, a pre-deployment script was run to test that the internal electronics were performing correctly and to set-up the instrument deployment. The instruments were configured to have standard 25 x 8 m bins, with one water track and one bottom track ping in a two second ensemble and no blanking distance.

Data Processing

After each cast, the binary files recorded by the instrument were downloaded onto the local computer. TRDI WinADCP 1.14 software was used to record the number of pings (ensembles), check the data file start and end times, and check for consistent levels for all four beams of echo intensity and beam correlation. All data were processed using MATLAB code developed at Lamont-Doherty Earth Observatory (LDEO) by Martin Visbeck and updated by Andreas Thurnherr, known as the LDEO IX method (Version LDEO_IX.7). This method obtains bottom track profiles and monitors instrument beams to calculate velocity based on both shear and inversion methods. Processing was carried out using two sets of constraints:

• Ship navigation (GPS) for stations 1 - 16 only
• Vessel-Mounted ADCP (VMADCP) for stations 17 onwards

Shallow profiles (<1500 m) from stations 1 - 16 were constrained to GPS data only to provide depth integrated velocity estimates. Whereas the deeper profiles (>1500 m) from stations 17 onwards were constrained only to the VMADCP as the GPS constraint could introduce noise into the surface and bottom sections of the deeper profiles. Northward and eastward velocity data from both shallow and deep profiles were binned at every 5 m depth, and cleaned up at the surface 100 m and point of maximum depth of the profiles. During the cleaning up, data values were flagged and nulled based on the following variable limits: vel_err > 0.2; nvel < 10; uerr > 0.15. The cleaned up variables for each station were renamed "u_new" and "v_new", then appended to the other LDEO output variables and saved together as a netCDF file.

Additional Information

LADCP's were switched off during shallow water casts (<200 m) stations 2 -4 due to noisiness. The LADCP's were also removed from the rosette for deep water casts (> 6000 m) stations 67 - 70 as the instruments were not pro-rated for water deeper than 6000 m. File availability and other issues with performance were noted. There was no slave data for stations 10, 18, 23 and 51. The data from station 25 was merged with station 26. Issues with interrupted/truncated LADCP files for stations 51 and 53 prompted the NMF team to switch cables (effective starting from station 54). Due to poor beam performance, the upward-looking LADCP was swapped from s/n 13399 to s/n 24465 at station 71 prior to deployment. After station 71, it appeared as if no data were being recorded by the upward-looking LADCP and that the compass was stuck at the same reading. Further investigation determined that the downward-looking LADCP had the wrong timestamp in it, and when processing the downlooker and uplooker together, it caused the uplooker to appear as if it were not functioning. The issue was corrected and new files were produced.

Further information on the LADCP processing can be found in pages 39-41 and 127-145 of Sanchez-Franks (2020).

References

Sanchez-Franks, A. (2020) RRS James Cook Cruise JC191, 19 January - 01 March 2020. Hydrographic sections from the Florida Straits to the Canaries Current across 24°N in the Atlantic Ocean. Southampton, UK: National Oceanography Centre, Southampton, 262 pp. (National Oceanography Centre Cruise Report, No 70)

Project Information

Marine LTSS: CLASS (Climate Linked Atlantic Sector Science)

Introduction

CLASS is a five year (2018 to 2023) programme, funded by the Natural Environment Research Council (NERC) and extended until March 2024.

Scientific Rationale

The ocean plays a vital role in sustaining life on planet Earth, providing us with both living resources and climate regulation. The trajectory of anthropogenically driven climate change will be substantially controlled by the ocean due to its absorption of excess heat and carbon from the atmosphere, with consequent impacts on ocean resources that remain poorly understood. In an era of rapid planetary change, expanding global population and intense resource exploitation, it is vital that there are internationally coordinated ocean observing and prediction systems so policy makers can make sound evidence-based decisions about how to manage our interaction with the ocean. CLASS will underpin the UK contribution to these systems, documenting and understanding change in the marine environment, evaluating the impact of climate change and effectiveness of conservation measures and predicting the future evolution of marine environments. Over the five-year period CLASS will enhance the cost-effectiveness of observing systems by migrating them towards cutting edge autonomous technologies and developing new sensors. Finally, CLASS will create effective engagement activities ensuring academic partners have transparent access to NERC marine science capability through graduate training partnerships and access to shipborne, lab based and autonomous facilities, and modelling capabilities.

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

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

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

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:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Appendix 1: 24.5 degrees N Hydrographic Transatlantic section - A05

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.