Metadata Report for BODC Series Reference Number 2310308

• 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

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

Narrative Documents

Nortek Aquadopp Open Water Current Meter

This instrument provides 3D acoustic doppler current measurements along with standard measurements of temperature, pressure, tilt and direction. It can be used in real time measurement situations or can log to an internal recorder powered by internal batteries. It can also be configured to measure surface wave height, period and direction concurrently. It has the unique feature of being run in 'diagnostic' mode when set to collect data at 1 Hz frequency in user specified intervals. This allows studies of mooring motion and the performance of other current meters to be conducted. It can be set in various configurations with titanium housings for deployment at greater depths.

Standard Measured Parameters

• 3D current velocity (East/North/Up, X/Y/Z or Beam 1/2/3)

• Acoustic signal strength (Beam 1/2/3)

• Compass

• Tilt

• Temperature

• Pressure

• Battery voltage

• Status code

• Error code

Surface wave monitoring

The standard Aquadopp is suitable for measuring surface wave height, period, and direction, which are calculated using the PUV method whereby spectra are estimated based on a combination of the pressure signal recorded by the instrument (P) and two horizontal components of the wave orbital velocity (U and V). More specifically, the pressure signal is used to provide an estimate of the wave frequency spectrum. The energy in this spectrum is then used to estimate wave height and period. The measurements of the wave orbital velocities are used to provide an estimate of the wave direction. Since these estimates are based on the distribution of wave energy and are not direct measurements of the free surface, they should be considered inferred estimates.

Both the dynamic pressure and the orbital velocities are driven by surface waves. The signals that are associated with these properties are complicated by the fact that they attenuate (that is the signals are weaker) with depth. The exact behaviour of the attenuation is determined by the water depth and the wavelength being observed. The greater the water depth the greater the attenuation; likewise, the shorter the wavelength (or higher the frequency of the wave) the greater the attenuation for a given water depth. This means that the estimation of wave parameters is limited by both water depth and wave frequency.

Specifications

Further details can be found in the manufacturer's specification sheets for the Aquadopp, Aquadopp 3000 and Aquadopp 6000.

BODC processing of Nortek moored current meter data from cruise JC238, UK-OSNAP / Ellett Array moorings IB4 and IB5, July 2022 to July 2024

The mooring data were supplied to BODC as ASCII files and converted to BODC internal format (QXF). During transfer the originator's variables were mapped to unique BODC parameter codes. The following table shows the parameter mapping:

Following transfer the data were screened using BODC in-house visualisation software.

Both moorings pressure records showed a series of knockdown events, more frequently in the winter time, with a particularly large event (>100dbar pressure change) affecting IB4 for two weeks in November 2022. Dataset users are encouraged to assess the instruments pressure record (PREXPR01) rather than rely solely on the nominal instrument deployment depth.

The following data issues were noted:

• Serial number 11979 (IB4): 2 vertical velocity values appeared suspect (values over 20 cm/s, over 10 standard deviations away from the mean). The data points were flagged (BODC flag M).
• Serial number 12047 (IB4): the instrument recorded pitch values over 30 degrees for 6 consecutive data points during the large November 2022 knockdown. The instrument manufacturer advises that velocity data is in general not reliable and should be discarded when the instrument is tilted by 30 degrees or more; therefore the eastward, northward and vertical velocity values for those data points were flagged (BODC flag M). The manufacturer also notes potential data quality issues when the instrument tilt is over 20 degrees; BODC has not flagged these data points but users are advised to perform their own assessment of pitch and roll.

Originator processing of Nortek moored current meter data from cruise JC238, UK-OSNAP / Ellett Array moorings, July 2022 to July 2024

Sampling Strategy

During the RRS James Cook cruise JC238, Nortek Aquadopps were deployed on the UK-OSNAP Rockall Trough moorings: 6 at the RTEB1 site, 5 at the RTWB1 site, and 3 at the RTWB2 site. Additionally, Nortek Aquadopps were deployed on the UK-OSNAP Iceland Basin moorings: 3 at the IB3 site, 3 at the IB4 site, and 2 at the IB5 site.

Prior to deployment, their clocks were synchronised with GPS time, new batteries fitted, and a functional check was performed. They were set to record temperature, pressure, velocity, heading, pitch, and roll every hour.

These moorings were recovered during the RRS Discovery cruise DY181.

Data Acquisition and Initial Processing

After recovery the data were downloaded from the instruments and the clock offsets checked with no significant drift found. One instrument (Serial Number 11021 on IB4) was flooded and the data could not be retrieved. For the remaining datasets the following processing steps were followed:

1. Removal of launch and recovery periods from dataset.
2. Correction for magnetic declination.
3. Correction for sound speed.
4. Automatic de-spiking using a spike/mean ratio of 10.

After recovery, the compass data for SN 6273 (1770 m) from EB1 appeared suspicious, therefore all data from this sensor were considered bad. Data for this sensor was subsequently omitted, and the remaining 5 sensors' data were retained.

More detailed information regarding the processing can be found in the DY181 cruise report on pp. 67-70.

The processed data were supplied to BODC for banking.

Project Information

UK - Overturning in the Subpolar North Atlantic Programme (UK-OSNAP) Programme

UK-OSNAP is part of an international collaboration to establish a transoceanic observing system in the subpolar North Atlantic. The aim is to quantify and understand the Subpolar Gyre's response to local and remote forcing of mass, heat and freshwater fluxes, within the conceptual framework of the Atlantic Meridional Overturning Circulation (AMOC).

UK-OSNAP is developing a new observing system to provide a continuous record of full-depth, trans-basin mass, heat, and freshwater fluxes. Combining these sustained measurements with innovative modelling techniques will enable the project to characterise the circulation and fluxes of the North Atlantic Subpolar Gyre.

UK-OSNAP is funded by the Natural Environment Research Council (NERC). The project is led by the National Oceanography Centre (NOC) with partners in the University of Liverpool, the University of Oxford and the Scottish Association for Marine Science (SAMS). It is a part of international OSNAP that is led by USA and includes 10 further partner groups in Canada, France, Germany, the Netherlands and China. The project involves fieldwork at sea and model studies.

The OSNAP observing system consists of two legs: one extending from southern Labrador to the southwestern tip of Greenland across the mouth of the Labrador Sea (OSNAP West), and the second from the southeastern tip of Greenland to Scotland (OSNAP East). The observing system also includes subsurface floats (OSNAP Floats) in order to trace the pathways of overflow waters in the basin and to assess the connectivity of currents crossing the OSNAP line.

NERC have added an extension to UK-OSNAP, until October 2024. This will result in the UK-OSNAP-Decade: 10 years of observing and understanding the overturning circulation in the subpolar North Atlantic (2014-2024). UK-OSNAP Decade forms part of the wider UK-OSNAP programme. Although supported through separate funding streams, including the Collective Funds 'Changing North Atlantic' grant, OSNAP decade (NE/T00858X/1), is considered a continuation of the core programme. In line with this, activities and associated data are grouped under UK-OSNAP, with funding details recorded here rather than as a separate project.

Marine LTSS: CLASS (Climate Linked Atlantic Sector Science)

Introduction

CLASS is a five year (2018 to 2023) programme, funded by the Natural Environment Research Council (NERC) and extended until March 2024.

Scientific Rationale

The ocean plays a vital role in sustaining life on planet Earth, providing us with both living resources and climate regulation. The trajectory of anthropogenically driven climate change will be substantially controlled by the ocean due to its absorption of excess heat and carbon from the atmosphere, with consequent impacts on ocean resources that remain poorly understood. In an era of rapid planetary change, expanding global population and intense resource exploitation, it is vital that there are internationally coordinated ocean observing and prediction systems so policy makers can make sound evidence-based decisions about how to manage our interaction with the ocean. CLASS will underpin the UK contribution to these systems, documenting and understanding change in the marine environment, evaluating the impact of climate change and effectiveness of conservation measures and predicting the future evolution of marine environments. Over the five-year period CLASS will enhance the cost-effectiveness of observing systems by migrating them towards cutting edge autonomous technologies and developing new sensors. Finally, CLASS will create effective engagement activities ensuring academic partners have transparent access to NERC marine science capability through graduate training partnerships and access to shipborne, lab based and autonomous facilities, and modelling capabilities.

Marine LTSS: AtlantiS (Atlantic Climate and Environment Strategic Science)

Introduction

AtlantiS is a five year (2024 to 2029) programme, funded by the Natural Environment Research Council (NERC).

Scientific Rationale

The global ocean is the largest part of the Earth's climate system and acts as a major buffer to climate changes resulting from human activities. By absorbing 90% of excess heat and nearly a quarter of carbon resulting from anthropogenic greenhouse gas emissions, the ocean has already substantially mitigated climate change in the atmosphere and on land. However, this service has come at a cost to the health and resilience of the ocean and by extension the people who depend on it. Significant damage has been caused to biodiversity and productivity of marine ecosystems, to shelf seas and coastal environments, and to inland areas through extremes of weather. The futures of regional climate and ecological systems depend on the response of the ocean to multiple anthropogenic stressors. Understanding and predicting the response is fundamental for sustainable development and to guide adaptation and mitigation.

The challenge is that the ocean is so large and variable that it cannot be completely and fully observed. Achieving adequate knowledge on all scales requires international coordination of observing and modelling over decades. It requires advancement in technology to expand our ability to observe beyond individual ships. It requires expanding the range of variables measured to include biogeochemistry and ecology. The opportunity now is to lead new capability to combine observations from a widening range of platforms and sensors, next-generation ocean and coupled models, and innovation in digital tools to meet the goal above. A range of national and international reviews have identified priority knowledge gaps related to natural and anthropogenically driven changes in the global ocean and the Atlantic and its shelf seas, and their impacts on marine ecosystems and human society:

• how natural and anthropogenic drivers of basin and decadal changes alter the Atlantic ecosystem, and the consequences for ecosystem functioning and services;
• the importance of ocean-shelf-coast connectivity in shaping ecosystems, biodiversity, natural hazards and impacts on society;
• the implications and feedbacks associated with climate mitigation strategies, and the need for improved assessments and advice to policy makers;
• the sensitivity and timescales of feedbacks that determine the ability of the ocean to continue to mitigate climate change by absorbing excess heat and carbon.

The aim of the AtlantiS programme is to provide evidence, tools and knowledge to support the ambition for healthy, biologically diverse and resilient marine environments, a sustainable blue economy and communities safe from natural hazards. The objectives are to strengthen the capacity of UK marine science to observe, model and predict the ocean through a step change in capability to maximise the value inherent in marine data; to transform the ocean from being data poor to data rich; to provide global syntheses of iconic climate change indicators; to lead an increase in public and government understanding of the role of the ocean in climate; and to communicate actionable knowledge effectively. AtlantiS is the continuation and development of the CLASS programme, enhancing the long-term, large-scale ocean observation systems and the ocean value-chain that contributes to key national and international programmes and priorities.

Data Activity or Cruise Information

Data Activity

Ellett Array Moored Instruments IB4 2022-2024

This rig was deployed as part of the Iceland Basin Array.

The rig was held down by a 1900 kilogram anchor on the seabed at 2919 metres depth. It was kept erect by 44" syntactic float at 75 metres depth and 2 glass spheres at 45 metres depth.

The instruments deployed on the rig were as follows:

Issues with mooring and sensors

The oxygen sensor failed at the start of the cal-dip on MicroCAT SMP-CTP-ODO S/N 12908 (349 m). Temperature and conductivity data are unaffected.
The Nortek Aquadopp S/N 11021 (1496 m) was found to be flooded (water ingress at bulkhead connector) and the data could not be retrieved.
The downward looking RDI WorkHorse 300kHz ADCP S/N 24589 was recovered flooded with its pressure sensor missing. No data were recovered.

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

UK-OSNAP/Ellett Array Mooring IB4 (OM54)

Mooring IB4 forms part of the OSNAP-East Transect and of the Ellett Array. It was first deployed in summer 2014 by the University of Miami. The mooring management and maintenance switched to the UK-OSNAP Community in July 2018.

It is located at the nominal location 58.00°N, 21.14°W in a water depth of 2920 m.

The mooring has been funded as part of the Ellett Array by UK-OSNAP (UK - Overturning in the Subpolar North Atlantic), CLASS (Climate Linked Atlantic Sector Science) and AtlantiS (Atlantic Climate and Environment Strategic Science).

Related Fixed Station activities are detailed in Appendix 2

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:

Appendix 1: IB4_03_2022

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.

Appendix 2: UK-OSNAP/Ellett Array Mooring IB4 (OM54)

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.