Metadata Report for BODC Series Reference Number 1899975

• 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

ACES-FOCAS James Clark Ross Cruise JR20070226 (JR165, JR170, JR174) Underway Navigation and Bathymetry Data Quality Document

Position

There were two speed fails identified creating gaps in the positional information. The affected cycles were nullified, positions were re-derived and flagged T (interpolated).

Ship's orientation

Data collection for ship's orientation began on 06 April 2007 and does not cover the entire series. Several M (suspect) flags were added to HEADCM01 where anomalous changes in ship's orientation were identified.

Bathymetry

The single beam bathymetry channel (MBANZZ01) and multi beam bathymetry (MBANSWCB) were compared along with the GEBCO depth channel as a reference source (MBANGB08). Both channels contain noise, however, the multi-beam bathymetry channel was a shorter time series and turned off for some of the cruise. Therefore the single beam echo sounder was considered by BODC to provide the overall best time series of bathymetry from this cruise. Although the single beam bathymetry channel is noisy there is a distinct bathymetry line. Regular drop out values of 0 have been flagged 'N'. The dataset has been cleaned up by applying 'M' flags to obvious spikes that cause a break in the flow of the bathymetry. Generally, the bathymetry is fine with fairly good agreement with GEBCO.

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

Kongsberg EA600 Single Beam Echosounder

The EA600 is a single beam echosounder with full ocean depth capability designed for bathymetric surveys. It measures water depth by monitoring the travel time of an acoustic signal that is transmitted from the ship, reflected off the seabed and received back at the ship.

The main components of the system are hull-mounted transducers linked to general purpose transceivers (GPTs). Up to four GPTs, each controlling one or more transducers, may be operated simultaneously. The GPT generates a signal, which is transmitted into the water column as an acoustic pulse by the transducer array, and the returning echo is recorded by the GPT. GPTs are in turn linked to a combined display and processor, where adjustments (such as sound-speed corrections) may be applied to the data. Available frequencies span from 12 to 710 kHz, and each GPT may operate at a separate frequency. A variety of transducers is available for water depths up to 11,000 m.

The EA600 stores all data internally but has a USB port which allows the possibility of connecting a CD-ROM/DVD drive to read and write the data. All echo data can be stored as files: bitmap, sample, depth or sidescan data.

In deeper waters, the EA600 supports a multipulse function, allowing for a higher pinger rate. While on passive mode, the pinger is normally attached to a device, with the purpose of tracking and displaying its current depth.

The EA600 replaced the EA500 in 2000.

Specifications

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

Kongsberg Seatex Seapath 200 GPS and Gyrocompass

The Seapath 200 is a highly accurate, real-time heading, attitude and position information system that integrates the best signal characteristics of Inertial Measurement Units (IMU) and Global Positioning System (GPS), using a differential GPS method to acquire this data.

The high-rate motion data is obtained from the Seatex MRU5 inertial sensor and two fixed baseline GPS carrier-phase receivers. The raw data is integrated in a Kalman filter in the Seapath Processing Unit. The IMU contains an accurate linear accelerometer and Bosch Coriolis force angular rate gyros (CFG).

This system is equipped to utilise up to six different DGPS reference stations, it checks for consistency within measurements from the different sensors to ensure reliability and rejects noisy data or reports its inaccuracy. The data is available through various output protocols, RS-232, RS-422 and Ethernet.

This instrument is no longer in production; the main characteristics are presented below, and the specification sheet can be accessed here Kongsberg Seatex Seapath 200 .

Specifications

Sperry Marine MK-37 Gyrocompass

A family of instruments that contain a controlled gyroscope which seeks and aligns itself with the meridian and points to true north. They use the properties of the gyroscope in combination with the rotation of the earth and the effect of gravity. The effects of varying speed and latitude are compensated for by the use of manually operated controls. Models MOD I, MOD O, MOD D, MOD D/E are all with an analog output Step or/and Syncro. MOD VT is the latest model with NMEA Data output as well.

Further specifications for MOD VT can be found in the manufacturer's specification document.

Further information for MOD D/E can be found in the user manual.

RRS James Clark Ross Cruise JR20070226 (JR165, JR170, JR174) Navigation Instrumentation

The following scientific navigational and bathymetric systems were fitted. The final file contains data from the Seatex GPS as it is the GPS used for the multibeam positioning, and is therefore deemed the most accurate.

ACES-FOCAS Cruise RRS James Clark Ross JR20070226 (JR165, JR170, JR174) Underway Navigation and Bathymetry Processing Procedures Document

Originator's Data Processing

Four files with processed data and one file with raw data were received at BODC. Data collection started on 26 February 2007 12:48 hours and ended on 17 April 2007 20:12 hours.

Bathymetry data were not processed by the originator and were retrieved from raw files.

The originator's procedures implemented throughout the cruise consisted of data retrieval from the previous 24h and logging those into subdirectories on the ship's intranet system.

Navigation instruments were located on the ship's monkey island, above the bridge.

Data processing was carried out at BAS on selected data streams. The ship has four positioning systems, but as the Seatex GPS provides the input latitude and longitude for the multibeam positioning, it is considered as a primary source of data, so processing was carried out on this stream but not on the others.

The processing procedures carried out by the originator include:

• check for duplicate dates and times
• standardising time
• check for gaps in data
• check data against defined thresholds
• interpolation and flagging
• unit conversion

Files delivered to BODC

* Please note that although the file is called em120, the instrument model is actually an em122

BODC Data Processing

The files mentioned above were selected for data banking as they contain the best version of processed position, heading and bathymetry. Data were banked at BODC following standard data banking procedures, including reduction through averaging, checking navigation channels for improbable values, working out speed over ground, and screening the data for anomalous values.

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

jr165_seatex_exactsec

The file also contained vn, ve, cmg, smg, dist_run v_minus_1, however these parameters were not transferred as they were derived by the originator or could be extracted from a more accurate source.

jr165_gyro_exactsec

ea600

BODC's procedures included the transfer of originator's parameters into BODC codes and visual screening in Edserplo. N flags were applied to absent values during the data transfer.

Position

2 speed fails were identified during checks. The affected cycles were nullified and positions re-derived following established procedures.

Ship's eastward and northward velocities were calculated from the main latitude and longitude channels.

Ship's orientation

HEADCM01 was screened and several M flags were assigned to cycles were anomalous changes in ship's orientation were identified. The data collected with this instrument does not cover the entire cruise, as it only starts on 06 April 2007 12:34.

Distance run

Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the cruise period.

Bathymetry

Bathymetry data from the multibeam and single beam echosounders were loaded and screened. Several M flags were applied to both channels where drops in data were identified as anomalous. The single beam data (MBANZZ01) has slightly more data than the multibeam, therefore it is considered to be the overall best time series of bathymetry for this cruise and the multibeam channel was dropped from the final file.

Project Information

ACES- Antarctic Climate and the Earth System

Introduction

This project is part of the BAS GSAC five year research programme. It was funded by NERC and extended from 2005 to 2009.

ACES aims to investigate the atmospheric and oceanic links that connect the climate of the Antarctic to that of lower latitudes, and their controlling mechanisms. Specific research topics include the formation and properties of Antarctic clouds, the complexities of the atmospheric boundary layer and the importance to the global ocean circulation of cold, dense water masses generated in the Antarctic.

Data will be collected by a comprehensive programme of oceanographic measurements from BAS ships in the Weddell and Bellingshausen Seas and by the Twin Otter aircraft, which will allow for the study of cloud microphysics and air-sea-ice interaction. An ice core will be collected from the southwestern Antarctic Peninsula and will give a 150-year record of the strength of the circumpolar westerly winds. This data will be used to test and improve global climate models and a new regional atmosphere-ice-ocean model for the Antarctic.

ACES has two components: ACES-FOCAS (Forcings from the Ocean, Clouds, Atmosphere and Sea-ice) and ACES-ACCENT (Antarctic Climate Change and Nonlinear Teleconnections). It also links with several other projects: CACHE, GRADES, GEACEP, BIOFLAME, DISCOVERY2010 and SEC.

Scientific Objectives

The main objectives are:

• Understand the interactions between atmosphere, sea-ice and ocean at high southern latitudes
• Develop models to aid our understanding of Antarctic regional processes and enable the representation of essential regional phenomena in global models covering both the atmosphere and ocean
• Determine the nature and influence of the principal connections between Antarctica and the global climate system
• Determine the importance of water masses of Antarctic origin in the global ocean circulation
• Determine the sensitivity of the global climate system to processes occurring or originating in the Antarctic

Data Availability

Data sets collected during this project are available to the academic community.

Acronyms used in this text:

BAS- British Antarctic Survey

GSAC- Global Science in an Antarctic Context

CACHE- Climate and Chemistry: forcings , feedbacks and phasings in the Earth System

GRADES- Glacial retreat in Antarctica and Deglaciation of the Earth System

GEACEP- Greenhouse to ice-house: Evolution of the Antarctic Cryosphere and Paleoenvironment

BIOFLAME- Biodiversity, Function, Limits and Adaptation from Molecules to Ecosystems

DISCOVERY2010- Integrating Southern Ocean Ecosystems into the Earth System

SEC- Sun Earth Connections Programme

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: