Metadata Report for BODC Series Reference Number 1044326

• 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

Kongsberg Simrad EA500 bathymetric echosounder

The EA500 is a bathymetric echosounder that can be used in water as deep as 10,000 m. It features triple frequency operation with a separate digitiser for each channel and high transmitted power with an instantaneous dynamic range of 160 dB. The instrument can operate with several pulses in the water simultaneously and has bottom tracking capabilities. A wide range of transducers (single beam, split beam or side-looking) is available and the ping rate is adjustable up to 10 pings per second. The split beam operation measures the athwartships inclination angle of the seabed.

This instrument was introduced in June 1989 and and replaced by the EA 600 in 2000.

Specifications

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

RAPID Cruise D298 Underway Navigation and Bathymetry Instrumentation

There are four GPS receivers on RRS Discovery: the Trimble 4000, which is a differential GPS; the Glonass, which uses a combination of Russian and American satellite networks; the Ashtech; and the SeaStar G12.

Two sources of bathymetric data were available on this cruise; a Precision Echosounding (PES) hull mounted fish transducer; and a Simrad EA500 hydrographic echosounder.

RAPID Cruise D298 Underway Meteorology, Surface Hydrography and Navigation Series

Cruise Details

D298 was conducted in the vicinty of Cape Farewell, southern Greenland, during early autumn 2005. The main priority of the cruise was to complete a number of mooring operations, but this work was combined with additional hydrographic survey work, sediment coring and sub-bottom profiling.

Data Processing Procedures

Underway sea surface hydrography, meteorology and ship's navigation data are merged into common files using time (UTC) as the primary linking key. Any additional data calibrations are applied as appropriate and are discussed in the individual instrument sections.

Data were transferred to BODC's in-house NetCDF format, QXF, through the BODC Underway Data System (BUDS). During transfer data were time averaged to 120 second intervals. The transfer process also includes the flagging of data which fall outside of the range of acceptable values for each parameter.

Each data channel is visually inspected on a graphics workstation and any spikes or periods of dubious data are flagged as suspect. The capabilities of the workstation screening software allows all possible comparative screening checks between channels. The system also has the facililty of simultaneously displaying the data and the ship's position on a map to enable data screening to take oceanographic climatology into account.

RAPID Cruise D298 Underway Navigation and Bathymetry Processing

Originator's processing

Although all four navigation streams were logged during the cruise, navigation data were obtained from the preferred Trimble 4000 GPS receiver and, where gaps occurred, from Glonass. These data were processed via the PSTAR 'bestnav' procedure. A major problem occurred with the master clock signal used by all navigation streams which was corrected, however there may be still be problems for data before 30th August 2005.

Bathymetric depth by towed fish echosounder was preferred by the originator over the Simrad EA500 echosounder. The data were corrected onboard using Carters tables.

Data were transferred from the raw RVS format to PSTAR format using unix command scripts and compiled into 2 minute averages.

BODC processing

Navigation was checked for gaps and improbable ship speeds at BODC. No improbable speeds were found. Any gaps were linearly interpolated to provide a continuous data record.

Distance run was calculated using latitude and longitude at BODC.

Bathymetric depth from the GEBCO Centenary 1-Minute Global Grid was merged into the file as a supplementary source of bathymetry for comparison purposes.

Project Information

Rapid Climate Change (RAPID) Programme

Rapid Climate Change (RAPID) is a £20 million, six-year (2001-2007) programme of the Natural Environment Research Council (NERC). The programme aims to improve our ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.

Scientific Objectives

• To establish a pre-operational prototype system to continuously observe the strength and structure of the Atlantic Meridional Overturning Circulation (MOC).
• To support long-term direct observations of water, heat, salt, and ice transports at critical locations in the northern North Atlantic, to quantify the atmospheric and other (e.g. river run-off, ice sheet discharge) forcing of these transports, and to perform process studies of ocean mixing at northern high latitudes.
• To construct well-calibrated and time-resolved palaeo data records of past climate change, including error estimates, with a particular emphasis on the quantification of the timing and magnitude of rapid change at annual to centennial time-scales.
• To develop and use high-resolution physical models to synthesise observational data.
• To apply a hierarchy of modelling approaches to understand the processes that connect changes in ocean convection and its atmospheric forcing to the large-scale transports relevant to the modulation of climate.
• To understand, using model experimentation and data (palaeo and present day), the atmosphere's response to large changes in Atlantic northward heat transport, in particular changes in storm tracks, storm frequency, storm strengths, and energy and moisture transports.
• To use both instrumental and palaeo data for the quantitative testing of models' abilities to reproduce climate variability and rapid changes on annual to centennial time-scales. To explore the extent to which these data can provide direct information about the thermohaline circulation (THC) and other possible rapid changes in the climate system and their impact.
• To quantify the probability and magnitude of potential future rapid climate change, and the uncertainties in these estimates.

Projects

Overall 38 projects have been funded by the RAPID programme. These include 4 which focus on Monitoring the Meridional Overturning Circulation (MOC), and 5 international projects jointly funded by the Netherlands Organisation for Scientific Research, the Research Council of Norway and NERC.

The RAPID effort to design a system to continuously monitor the strength and structure of the North Atlantic Meridional Overturning Circulation is being matched by comparative funding from the US National Science Foundation (NSF) for collaborative projects reviewed jointly with the NERC proposals. Three projects were funded by NSF.

A proportion of RAPID funding as been made available for Small and Medium Sized Enterprises (SMEs) as part of NERC's Small Business Research Initiative (SBRI). The SBRI aims to stimulate innovation in the economy by encouraging more high-tech small firms to start up or to develop new research capacities. As a result 4 projects have been funded.

RAPID - Cape Farewell and Eirik Ridge: Interannual to Millennial Thermohaline Circulation Variability

This project was funded under the NERC Rapid Climate Change Programme, grant number NER/T/S/2002/00453. Dr. Sheldon Bacon (Southampton Oceanography Centre) was the Principal Investigator, with co-Investigators from the University of Southampton, Prof. D. A. Stow and Dr. E. J. Rohling. The project started in December 2003 and ended in November 2008.

The project used a combination of hydrography and palaeoceanography measurements to determine the spectrum of variability of the Deep Western Boundary Current, on timescales from days to millennia. The project focused on deglacial to Holocene variability; in particular, seeking to characterise the onset and endings of three cold periods: the Younger Dryas (YD; 12.5-11.5 ka BP), the ~8.2 ka event, and the Little Ice Age (LIA; 16th-19th century AD).

The objectives of the project included:

• Defining the THC response to Holocene climate variability by a highly resolved investigation of palaeoceanographic/climate proxies in sediment cores
• Developing high-resolution sediment proxies for bottom current speed
• Absolute calibration of sediment proxies for bottom current speed
• Defining the relationship between drift construction and the bottom current regime
• Improved definition of present-day ocean circulation and climate

Most of the fieldwork was carried out on 2 cruises in the Cape Farewell and Irminger Sea vicinity:

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: