Metadata Report for BODC Series Reference Number 2012137

• 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

JR16005 Underway Navigation Quality Control Report

Position

Position channels look good. Two gaps just at the start and end of the dataset, which can be trimmed off at the end of processing. flags were automatically applied to this.

Heading

Heading channel looks good. There are some large fluctuations within the permitted maximum and minimum parameter values and there are some parts of the datasets where absent values have been recorded. These absent values were automatically flagged.

Bathymetry

All bathymetry channels show a similar pattern. The quality of both the single-beam and the multi-beam channel are moderate as there are numerous dropouts and noisy periods. Despite this, both channels follow GEBCOâ??s trend very well once quality control flags had been applied.

The overall quality of the multi-beam is slightly better than the single beam and the multi-beam was also the preferred bathymetry channel selected by the originator. Thus, the multi-beam is the preferred source of bathymetry.

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

RRS James Clark Ross cruise JR16005 underway document

Cruise details

Kongsberg EM122 12kHz Multibeam Echosounder

The EM122 is designed to perform seabed mapping to full ocean depth with a high resolution, coverage and accuracy. Beam focusing is applied both during reception and transmission. The system has up to 288 beams/432 soundings per swath with pointing angles, which are automatically adjusted according to achievable coverage or operator defined limits.

This model uses both Continuous Wave and Frequency Modulated sweep pulses with pulse compression on reception, in order to increase the maximum useful swath width. The transmit fan is split in several individual sectors, with independent active steering, in order to compensate for the vessel movements.

In multiplying mode, two swaths per ping cycle are generated, with up to 864 soundings. The beam spacing is equidistant or equiangular and the transmit fan is duplicated and transmitted with a small difference in along track tilt, which takes into account depth coverage and vessel speed, to give a constant sounding separation along track. In high density mode, more than one sounding per beam can be produced, such that horizontal resolution is increased and is almost constant over the whole swath.

The EM122 transducers are modular linear arrays in a Mills cross configuration with separate units for transmit and receive. If used to deliver sub-bottom profiling capabilities with a very narrow beamwidth, this system is known as SBP120 Sub-Bottom Profiler.

The specification sheet can be accessed here Kongsberg EM122.

Specifications

EM122 versions

JR16005 Underway Navigation Instrumentation

The following scientific navigational and bathymetric systems were fitted.

Kongsberg Seatex Seapath 320+ Precise Heading, Attitude and Positioning Sensor

The Seapath 320+ is a navigational system that combines two Global Navigation Satellite System (GNSS) receivers with a MRU 5+ inertial sensor to provide high resolution and accuracy positional data. The inertial sensor employs linear accelerometers and unique microelectromechanical systems (MEMS)-type angular rate gyros to provide 0.01 RMS pitch and roll accuracy. The GNSS receivers can use multiple satellite constellations (GPS, GLONASS and Galileo, when available), and combine data from these to improve heading and positional measurements. In case of missing data from one GNSS receiver, the other receiver provides position and velocity, and the inertial sensor provides heading from its internal rate sensors.

The main characteristics are presented below, and the specification sheet can be accessed here Kongsberg Seatex Seapath 320+ .

Specifications

JR16005 Underway Navigation and Bathymetry Processing Procedures Document

Originator's Data Processing

The navigation and bathymetric data were measured by several different instruments and the data were logged every second to the SCS system and stored in comma separated ACO format. Each instrument logged data to one individual file and the associated header information is stored in TPL files.

The originator compiled the .ACO files into a MATLAB structure array for further processing. The originator's .MAT file includes navigation and bathymetry data. The .MAT file was provided to BODC and used for BODC processing.

The table below shows the original files delivered to BODC that contained the data in the final data series, along with start and end dates and times of each file.

BODC Data Processing

The data were reformatted to BODC internal format using standard banking procedures. Data were averaged at 60 second intervals. The following table shows how variables within the file were mapped to appropriate BODC parameter codes:

All the reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag.

Position

A check was run on positional data to identify gaps and improbable values (through the calculation of speed). Numerous gaps and speed fails were found. These were corrected by running a script that uses linear interpolation to fill in the gaps.

Ship velocities

Ship velocities were calculated from the main latitude and longitude channels using standard BODC procedures.

Distance Run

Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the file, using BODC standard procedures.

GEBCO

GEBCO bathymetry was added to the file using the main latitude and longitude channels.

Bathymetry

Bathymetry data were screened independently as well as against GEBCO bathymetry measurements. The mulit-beam echo sounder was deemed to be the best quality source of bathymetry and was retained in the file.

Calibration

No sample calibrations were applied to these data.

Project Information

Dynamics of Orkney Passage Outflow (DynOPO)

DynOPO is a five year research project that aims to understand how Antarctic Bottom Water is exported and modified through the Orkney Passage, the overflow's controlling dynamics, and its downstream impact on the Atlantic Ocean abyss.

Introduction

Mooring data collected for the DynOPO project are a component of a long term time series, in association with the Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA) project, led by Emily Shuckburgh (British Antarctic Survey) since 2016. The time series originally started out as part of the British Antarctic Survey's Long-Term Monitoring and Survey (LTMS) programme. Moorings were deployed on RRS James Clark Ross cruise JR20150309 (JR310 and JR272D) which ran from 09 March to 14 April 2015. RRS James Clark Ross cruise JR16005 ran from 17 March to 08 May 2017 and was the primary fieldwork element of the DynOPO project. The cruise had two main goals: (1) to conduct measurements of the hydrographic properties, velocity and turbulent processes of the Antarctic Bottom Water outflow along its pathway through the Orkney Passage region; and (2) to turn around a set of long-term moorings deployed in the area by British Antarctic Survey (BAS) and Lamont-Doherty Earth Observatory (LDEO) scientists, including recovery of additional instruments on some of the moorings deployed by JR20150309.

Project Collaborators

The project was led by the University of Southampton, and is an international collaboration with;

• UK: British Antarctic Survey (BAS), UK Meteorological Office, University of East Anglia and Newcastle University;
• Europe: University of Gothenburg (Sweden), University of Paris 6 (France);
• Australia: University of Tasmania;
• US: Lamont Doherty Earth Observatory, Woods Hole Oceanographic Institute, NOAA, University of California, Washington State University and Princeton University

Funding

The project was funded by the Natural Environment Research Council and ran from March 2015 to November 2018.

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: