Metadata Report for BODC Series Reference Number 1124326

• 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

Comments on XCTD data collected during cruise D318

During the screening of the XCTD data it was noticed that in two XCTD casts (C3_00016 and C3_00486), there appeared to be a three cycle delay in the response of derived channels salinity and sound velocity to changes in conductivity. It is unclear what the cause of the offset is or whether this problem affects other casts.

Data Quality

This data is also held by ICES, who have chosen to add additional data quality flags to the salinity data. BODC have not added these flags to the data held at BODC.

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

Lockheed Martin Sippican XCTD-1 probe

Lockheed Martin Sippican XCTD-1 probe

The expendable CTD profiling system uses an inductive conductivity sensor, thermistor and microprocessor based battery-powered circuitry to internally compute and average the temperature and conductivity of the water column. The XCTD is attached to a wire which is used to digitally transmit the data back to the research vessel. Time since the probe has entered the water is used as a proxy to calculate depth as the descent speed of the XCTD is known. During the manufacturing process the XCTD is calibrated at three temperatures and conductivities which are stored internally and used in the computation of temperature and conductivity prior to data transmission. After transmission the data is processed using the MK21 Data Acquisition System which is available in either ISA or USB configurations. The XCTD-1 Probe can be used within a maximum depth of 1000 m, with a rated ship speed of 12 knots. The full specification for this instrument can be found here.

Originator's processing document for D318 XCTD and XBT data

Sampling strategy

A total of 32 Lockhead Martin Sippican expendable conductivity, temperature and depth (XCTD) casts and 515 Lockhead Martin Sippican expendable bathythermograph (XBT) casts were conducted during RSS Discovery cruise D318, which took place in the Gulf of Cadiz (for more information see the D318 cruise report). The cruise was split up into two legs, D318a and D318b. D318a took place from 17 April 2007 to 23 April 2007, with D318b taking place from 27 April 2007 to 14 May 2007. Of the 32 XCTD casts, 22 were performed using XCTD-1 probes with the remaining 10 performed by XCTD-2 instruments. 496 of the 515 XBT casts were performed using XBT-T5 units with the remaining 19 being performed by XBT-T7 probes.

Deployment

Casts were performed at intervals of approximately 20 minutes. For the first two days every fifth cast was performed by an XCTD, however the use of XCTD probes became more sporadic from 20 April 2007, after the originator noticed spiking in the XCTD-2 data. This resulted in long periods of the cruise where only XBT-T5 instruments were used. The use of XCTDs became even more infrequent during leg D318b, with only 10 XCTD casts being performed.

During D318a, XBT and XCTD deployments occurred simultaneously with the deployment of a towed seismic array (air guns and hydrophone streamer). To combat the possibility of the XBT being entangled in the array the data originator rigged a guide pipe to keep the XBT wire further out on the starboard side of the RSS Discovery. This pipe comprised of around five metres of rubberised tubing with a diameter of approximately six centimetres, which was taped to a metal bar to keep it straight. One end was lashed to the rear starboard side of the ship with the other held outwards by the rear starboard crane at an angle of approximately 45° The lower end of the pipe was approximately three metres starboard of the rear of the ship, one to two metres above the sea surface. When launched the probes fell down the tube and into the sea below, away from the line of the towed array. Although this arrangement worked very well for the most part, some of the longer XCTD probes got stuck and needed to be shaken out of the tube.

Data from the XBT/XCTD sensors was transmitted up a length of copper wire to the Sippican data acquisition system. At the beginning of the cruise the old Sippican ISA data acquisition system was used to communicate with the XBTs and XCTDs, however this system started to pre-trigger the instruments before they hit the water. This led to the scientists switching to the USB system, which remained stable throughout the cruise.

Data processing

The originator processed the XBT and XCTD data for the following:

1) Determination of depth

XBTs and XCTDs measure depth as a proxy of elapsed descent time through the water column (this is a known variable). For D318, the XCTD depths were generated using the standard Sippican conversion equation. The Originator reports however, that for the XBT data the Sippican equation has been found to underestimate depth. They resolved this by using a more accurate equation proposed by Boyd and Linzell (1993) for the T5 and T7 XBTs. The originator reports that a temperature correction from Boyd and Linzell (1993) has also been applied to the XBT data. Additionally, the Originator derived sound velocity in both the XBT and XCTD data. For the XCTDs measured temperature and salinity data were used to compute sound velocity. For the XBTs, sound velocity was derived from the measured temperature data with an assumed constant salinity of 35 PSU.

2) Removal of bad data

The Data Originator reports that spiking was a persistent problem in some of the XCTD casts, rendering some portions of these data too troublesome to use. This was rectified by removing all data that the XCTD processing software flagged as bad data (those not given an 8000 flag by the Sippican software). Additionally, all XBTs which displayed persistent trends or peaks were also excluded from the data sent to BODC.

Calibrations

All XCTDs were purchased specifically for this cruise. Prior to transmission the data was calibrated using internally stored calibration coefficients calculated at three different temperatures and conductivities.

References

Boyd J.D., Linzell R.S., 1993. The Temperature and Depth Accuracy of Sippican T-5 XBTs. Journal of Atmospheric and Oceanic Technology. 10, pp 128-136.

Processing of D318 XCTD data by BODC

The Sippican XCTD data were supplied to BODC in the form of 32 ASCII files. Following standard BODC procedure, the data files were reformatted into BODC internal format using an internal transfer function. This table shows how the variables present in the XCTD data files were mapped to appropriate BODC parameter codes.

The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, missing data by both setting the data to an appropriate value and setting the quality control flag. In many of the XCTD casts, especially those performed by the XCTD-1 instrument, it was apparent that it took the conductivity sensor a few seconds to acclimatise. In these cases the first few cycles of the conductivity channel and any parameters derived from conductivity have been flagged.

General Data Screening carried out by BODC

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

• Irregularities such as unfeasible values
• Inconsistencies between related information, for example:
  • Times for instrument deployment and for start/end of data series
  • Length of record and the number of data cycles/cycle interval
  • Parameters expected and the parameters actually present in the data cycles
• Originator's comments on meter/mooring performance and data quality

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time or depth series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non-oceanographic origin may be tagged with the BODC flag denoting suspect value; the data values will not be altered.

The following types of irregularity, each relying on visual detection in the plot, are amongst those which may be flagged as suspect:

• Spurious data at the start or end of the record.
• Obvious spikes occurring in periods free from meteorological disturbance.
• A sequence of constant values in consecutive data cycles.

If a large percentage of the data is affected by irregularities then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought and, where necessary, documented. This covers inconsistencies such as the following:

• Maximum and minimum values of parameters (spikes excluded).
• The occurrence of meteorological events.

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

Project Information

Oceans 2025 Theme 3: Shelf and Coastal Processes

Over the next 20 years, UK local marine environments are predicted to experience ever-increasing rates of change - including increased temperature and seawater acidity, changing freshwater run-off, changes in sea level, and a likely increase in flooding events - causing great concern for those charged with their management and protection. The future quality, health and sustainability of UK marine waters require improved appreciation of the complex interactions that occur not only within the coastal and shelf environment, but also between the environment and human actions. This knowledge must primarily be provided by whole-system operational numerical models, able to provide reliable predictions of short and long-term system responses to change.

However, such tools are only viable if scientists understand the underlying processes they are attempting to model and can interpret the resulting data. Many fundamental processes in shelf edge, shelf, coastal and estuarine systems, particularly across key interfaces in the environment, are not fully understood.

Theme 3 addresses the following broad questions:

• How do biological, physical and chemical processes interact within shelf, coastal and estuarine systems, particularly at key environmental interfaces (e.g. coastline, sediment-water interface, thermocline, fronts and the shelf edge)?
• What are the consequences of these interactions on the functioning of the whole coastal system, including its sensitivity and/or resilience to change?
• Ultimately, what changes should be expected to be seen in the UK coastal environment over the next 50 years and beyond and how might these changes be transmitted into the open ocean?

Within Oceans 2025, Theme 3 will develop the necessary understanding of interacting processes to enable the consequences of environmental and anthropogenic change on UK shelf seas, coasts and estuaries to be predicted. Theme 3 will also provide knowledge that can improve the forecasting capability of models being used for the operational management of human activities in the coastal marine environment. Theme 3 is therefore directly relevant to all three of NERC's current strategic priorities; Earth's Life-Support Systems, Climate Change, and Sustainable Economies

The official Oceans 2025 documentation for this Theme is available from the following link: Oceans 2025 Theme 3

Weblink: http://www.oceans2025.org/

Oceans 2025 Theme 3, Work Package 3.1: Global Impacts of Shelf Seas

At the margins of the shelf seas, steep shelf-slope bathymetry has impacts on ocean circulation and the transmission of signals around the ocean basins (Hughes and Meredith, 2006), while dense water formation and cascades at the shelf edge are thought to be important for water mass formation (Ivanov et al., 2004) and for the off-shelf transport of organic and inorganic carbon (e.g. Wollast and Chou, 2001).

In this Work Package, the Proudman Oceanographic Laboratory (POL) aim to quantify the water fluxes between the shelf and open ocean globally, including the development of methods to incorporate shelf effects into global models. Greater understanding of the whole carbon cycle will benefit from combining this work on down-slope fluxes of water (and its constituent dissolved carbon) with work in Oceans 2025 Theme 5 (down-slope transports of sediments and particulate carbon).

The specific objectives are:

• Quantify and predict dense-water formation, cascading, slope mixing, their effects in the ocean
• Determine constraints that the ocean margin imposes on adjacent ocean circulation and fields
• Quantify and predict shelf seas' contribution to global biogeochemical budgets:
  • Ocean-margin fluxes and budgets of P, N, C, production and CO2
  • The shelf-ocean carbon "pump" (Yool and Fasham, 2001) and its dependence on context
  • The shelf seas' role in large-scale transport, especially of freshwater and pollutants

More detailed information on this Work Package is available at pages 5 - 27 of the official Oceans 2025 Theme 3 document: Oceans 2025 Theme 3

Weblink: http://www.oceans2025.org/

Some data used in Work Package 3.1 were collected to complement work carried out on the European Union's Geophysical Oceanography (GO) project. For these data, linkage to the GO project documentation is provided

References:

Hughes CW. and Meredith MP., 2006. Coherent sea level fluctuations along the global continental slope. Phil Trans Roy Soc A, 364, 885-901.

Ivanov VV., Shapiro GI., Huthnance JM., Aleynik DL. and Golovin PN., 2004. Cascades of dense water around the world ocean. Progr in Oceanogr, 60(1), 47-98.

Wollast R. and Chou L., 2001. Ocean margin exchange in the northern Gulf of Biscay: OMEX I. An introduction. Deep Sea Res II 48, 2971-2978.

Yool A. and Fasham MJR., 2001. An examination of the 'continental shelf pump' in an open ocean general circulation model. Global Biogeochem Cycles, 15, 831-844.

Oceans 2025 - The NERC Marine Centres' Strategic Research Programme 2007-2012

Who funds the programme?

The Natural Environment Research Council (NERC) funds the Oceans 2025 programme, which was originally planned in the context of NERC's 2002-2007 strategy and later realigned to NERC's subsequent strategy (Next Generation Science for Planet Earth; NERC 2007).

Who is involved in the programme?

The Oceans 2025 programme was designed by and is to be implemented through seven leading UK marine centres. The marine centres work together in coordination and are also supported by cooperation and input from government bodies, universities and other partners. The seven marine centres are:

• National Oceanography Centre, Southampton (NOCS)
• Plymouth Marine Laboratory (PML)
• Marine Biological Association (MBA)
• Sir Alister Hardy Foundation for Marine Science (SAHFOS)
• Proudman Oceanographic Laboratory (POL)
• Scottish Association for Marine Science (SAMS)
• Sea Mammal Research Unit (SMRU)

Oceans2025 provides funding to three national marine facilities, which provide services to the wider UK marine community, in addition to the Oceans 2025 community. These facilities are:

• British Oceanographic Data Centre (BODC), hosted at POL
• Permanent Service for Mean Sea Level (PSMSL), hosted at POL
• Culture Collection of Algae and Protozoa (CCAP), hosted at SAMS

The NERC-run Strategic Ocean Funding Initiative (SOFI) provides additional support to the programme by funding additional research projects and studentships that closely complement the Oceans 2025 programme, primarily through universities.

What is the programme about?

Oceans 2025 sets out to address some key challenges that face the UK as a result of a changing marine environment. The research funded through the programme sets out to increase understanding of the size, nature and impacts of these changes, with the aim to:

• improve knowledge of how the seas behave, not just now but in the future;
• help assess what that might mean for the Earth system and for society;
• assist in developing sustainable solutions for the management of marine resources for future generations;
• enhance the research capabilities and facilities available for UK marine science.

In order to address these aims there are nine science themes supported by the Oceans 2025 programme:

• Climate, circulation and sea level (Theme 1)
• Marine biogeochemical cycles (Theme 2)
• Shelf and coastal processes (Theme 3)
• Biodiversity and ecosystem functioning (Theme 4)
• Continental margins and deep ocean (Theme 5)
• Sustainable marine resources (Theme 6)
• Technology development (Theme 8)
• Next generation ocean prediction (Theme 9)
• Integration of sustained observations in the marine environment (Theme 10)

In the original programme proposal there was a theme on health and human impacts (Theme 7). The elements of this Theme have subsequently been included in Themes 3 and 9.

When is the programme active?

The programme started in April 2007 with funding for 5 years.

Brief summary of the programme fieldwork/data

Programme fieldwork and data collection are to be achieved through:

• physical, biological and chemical parameters sampling throughout the North and South Atlantic during collaborative research cruises aboard NERC's research vessels RRS Discovery, RRS James Cook and RRS James Clark Ross;
• the Continuous Plankton Recorder being deployed by SAHFOS in the North Atlantic and North Pacific on 'ships of opportunity';
• physical parameters measured and relayed in near real-time by fixed moorings and ARGO floats;
• coastal and shelf sea observatory data (Liverpool Bay Coastal Observatory (LBCO) and Western Channel Observatory (WCO)) using the RV Prince Madog and RV Quest.

The data is to be fed into models for validation and future projections. Greater detail can be found in the Theme documents.

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: