Metadata Report for BODC Series Reference Number 2047125

• 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 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

JC112 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

JC112 Underway Navigation Instrumentation

Instrumentation

The following scientific navigational and bathymetric systems were fitted.

Trimble Applanix Position and Orientation Systems for Marine Vessels (POSMV)

The Position and Orientation Systems for Marine Vessels (POSMV) is a real time kinematic (RTK) and differential global positioning system (DGPS) receiver for marine navigation. It includes an inertial system that provides platform attitude information. The instrument provides accurate location, heading, velocity, attitude, heave, acceleration and angular rate measurements.

There are three models of Applanix POSMV, the POS MV 320, POS MV Elite and the POS MV WaveMaster. POS MV 320 and POS MV WaveMaster are designed for use with multibeam sonar systems, enabling adherence to IHO (International Hydrographic Survey) standards on sonar swath widths of greater than ± 75 degrees under all dynamic conditions. The POS MV Elite offers true heading accuracy without the need for dual GPS installation and has the highest degree of accuracy in motion measurement for marine applications.

Specifications

POS MV 320

POS MV WaveMaster

POS MV Elite

¹ One Sigma, depending on quality of differential corrections
² Whichever is greater, for periods of 20 seconds or less

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

JC112 Navigation Data Processing Procedures

Originator's Data Processing

The data were logged by the TECHSAS (TECHnical and Scientific sensors Acquisition System) system into daily NetCDF files. The TECHSAS system is used as the main data logging system on NMF-SS operated reserach vessels. The daily TECHSAS NetCDF navigation and bathymetry files provided to BODC were used for BODC processing. Data were additionally logged into the RVS Level-C format files which have been archived at BODC.

Files delivered to BODC

BODC Data Processing

Data were banked at BODC following standard banking procedures. Data were averaged to 60 second intervals.

The originator's variables were mapped to appropriate BODC parameter codes as follows:

yyyymmdd-000000-position-Applanix_GPS_JC1.gps

yyyymmdd-000000-gyro-GYRO1_JC1.gyr

yyyymmdd-000000-sb_depth-EM120_JC1.depth

yyyymmdd-000000-EA600-EA600_JC1.EA600

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). There were drop outs in the positional data at the start and end of the file. These were flagged and trimmed after processing was complete.

Ship Velocities

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

GEBCO

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

Distance Run

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

Bathymetry

Bathymetry data were screened independently as well as against GEBCO bathymetry measurements. The EM120 was considered the source of bathymetric data during JC112 and was retained in the file.

Calibration

No field calibrations have been applied.

Project Information

Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge (OSCAR)

Background

The cooling of young oceanic crust is the main physical process responsible for removing heat from the solid Earth to the hydrosphere. Close to the mid-ocean ridge rapid cooling is dominated by hydrothermal circulation of seawater through the porous and fractured basalt crust. This hydrothermal fluid is then discharged into the ocean mainly along the ridge. Once in the ocean, released heated seawater mixes with the ambient cold water to form a plume, which provides a mechanism to lift the densest waters away from the bottom boundary layer. These waters are then more readily available for further mixing and heating as part of the global thermohaline circulation system.

The data collected as part of the interdisciplinary OSCAR project will be used to investigate the effects of heat loss and hydrothermal circulation in both the solid Earth and the ocean.

The aim is to:

1. Characterise how heat from the interior of the Earth is transported across the crust into the ocean by hydrothermal flows
2. Determine the impact the hydrothermal and geothermal fluxes have on the circulation of the abyssal ocean and on the evolution of the oceanic crust.

With this aim, the data will be used to derive a new integrated model of the ocean and hydrothermal circulations at active ocean ridges and ridge flanks. The model will be constrained by geophysical, geological, and physical oceanography data and include fluxes through a permeable seabed. These data and resultant models will set a new benchmark for integrated multi-physics experiments. They will result in a new understanding of the fluid and heat fluxes at ocean ridges and a better understanding of what geophysical and oceanographic data actually resolve in the context of an oceanic axial ridge setting. The result is also a predictive model that can be applied to similar ocean ridge systems world-wide.

Fieldwork

Data collection took place in the Panama Basin, bounded in the north-west by the Cocos Ridge, by the Carnegie Ridge in the south and by South and Central America in the east and north, respectively. Measurements were collected during RRS James Cook cruises JC112 and JC113 (05/12/2014 to 16/01/2015), RRS James Cook cruise JC114 (22/01/2015 to 08/03/2015) and RV Sonne cruise SO328 (06/02/2015 to 06/03/2015). Data were collected using Bottom Pressure Recorder, Acoustic Doppler Current Profiler (ADCP), Magnetotelluric Lander, CTD, Vertical Microstructure Profiler, Synthetic Aperture Radar, Ocean-bottom seismograph and Multibeam echosounder. Measurement of salinity, oxygen and helium were also made and zooplankton samples collected with vertical net casts.

Participants

• Professor Richard W Hobbs (Principal Investigator - Parent Grant) Durham University
• Professor Christine Peirce (Co-Investigator) Durham University
• Professor Christopher J Ballentine (Co-Investigator) University of Oxford
• Professor Joanna V Morgan (Co-Investigator) Imperial College London
• Dr Miguel Morales Maqueda (Principal Investigator - Child Grant) Newcastle University
• Dr David A Smeed (Co-Investigator - Child Grant) National Oceanography Centre
• Dr Vincent CH Tong (Principal Investigator - Child Grant) Birkbeck College

Funding

This project was funded by Natural Environment Research Council parent grant NE/I027010/1 and child grants NE/I022868/1, NE/I022868/2, NE/I022957/1, and NE/I022957/2, entitled 'OSCAR - Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge', with the former, parent grant led by Professor Richard W Hobbs, Durham University, and the latter child grants led by Dr Miguel Morales Maqueda, Newcastle University and Dr Vincent CH Tong, Birkbeck College.

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: