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Electrical conductivity of the water column

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  • For around a decade, southern elephant seals (mirounga leonina) have been used to collect hydrographic (temperature & salinity) profiles in the Southern Ocean. CTD-SRDLs (Conductivity Temperature Depth –Satellite Relayed Data Loggers) attached to seals' heads in Antarctic and sub-Antarctic locations measure water property profiles during dives and transmit data using the ARGOS (Advanced Research & Global Observation Satellite) network (Fedak 2013). CTD-SRDLs are built by the Sea Mammal Research Unit (SMRU, University of St Andrews, UK); they include miniaturised CTD units made by Valeport Ltd. When seals are foraging at sea 2.5 profiles can be obtained daily, on average. Profiles average 500m depth, but can be 2000m in extreme cases (Boehme et al. 2009, Roquet et al. 2011). Deployment efforts have been very intensive in the Southern Indian Ocean, with biannual campaigns in the Kerguelen Islands since 2004 and many deployments in Davis and Casey Antarctic stations (Roquet et al., 2013) more recently. 207 CTD-SRDL tags have been deployed there, giving about 75,000 hydrographic profiles in the Kerguelen Plateau area. About two thirds of the dataset was obtained between 2011 & 2013 as a consequence of intensive Australian Antarctic station deployments. There is also regular data since 2004 from French and Franco-Australian Kerguelen Island deployments. Although not included here, many CTD-SRDL tags deployed in the Kerguelen Islands included a fluorimeter. Fluorescence profiles can be used as a proxy for chlorophyll content (Guinet et al. 2013, Blain et al. 2013). Seal-derived hydrographic data have been used successfully to improve understanding of elephant seal foraging strategies and their success (Biuw et al., 2007, Bailleul, 2007). They provide detailed hydrographic observations in places and seasons with virtually no other data sources (Roquet et al. 2009, Ohshima et al. 2013, Roquet et al. 2013). Hydrographic data available in this dataset were edited using an Argo-inspired procedure and then visually. Each CTD-SRDL dataset was adjusted using several delayed-mode techniques, including a temperature offset correction and a linear-in-pressure salinity correction - described in Roquet et al. (2011). Adjusted hydrographic data have estimated accuracies of about +/-0.03oC and +/-0.05 psu (practical salinity unit). The salinity accuracy depends largely on the distribution of CTD data for any given CTD-SRDL, which decides the quality of adjustment parameters. Adjustments are best when hydrographic profiles are available in the region between the Southern Antarctic Circumpolar Current Front and the Antarctic divergence (55oS-62oS latitude range in the Southern Indian Ocean). Several institutes provided funding for the associated programs and the logistics necessary for the fieldwork. The observatory MEMO (Mammifères Echantillonneurs du Milieu Marin), funded by CNRS institutes (INSU and INEE), carried out the French contribution to the study. The project received financial and logistical support from CNES (TOSCA program), the Institut Paul-Emile Victor (IPEV), the Total Foundation and ANR. MEMO is associated with the Coriolis centre, part of the SOERE consortium CTD02 (Coriolis-temps différé Observations Océaniques, PI: G. Reverdin), which distributes real-time and delayed-mode products. The Australian contribution came from the Australian Animal Tracking and Monitoring System, an Integrated Marine Observing System (IMOS) facility. The work was also supported by the Australian Government's Cooperative Research Centres Programme via the Antarctic Climate & Ecosystem Cooperative Research Centre. The University of Tasmania and Macquarie University's Animal Ethics Committees approved the animal handling. Both tagging programs are part of the MEOP (Marine Mammals Exploring the Oceans Pole to Pole) international consortium - an International Polar Year (IPY) project.

  • The dataset comprises of vertical profiles of water column properties (temperature, salinity, conductivity, pressure, depth, sound velocity and density) of the full water column in the South West region of the UK. Measurements were taken opportunistically at three main locations (L4, L5 and E1 Western Channel Observatory stations) as well from Plymouth Sound and the surrounding inshore areas. Data have been gathered using a Valeport MIDAS 606 CTD (with a passive flow induction cell, Platinum Resistance Thermometer and a strain gauge transducer) and extracted and processed using Valeport DataLogX2 software (version1.0.4.1270). The CTD was deployed using vertical deployment from the RV MBA Sepia and were hauled using a manually controlled hydraulic winch. The surveyors have been dependent on the sensor calibrations applied by the CTD manufacturer (Valeport). Manufacturer calibrations are applied to the in situ direct measurements via sensor specific microchips in the CTD unit. Derived parameters are calculated using the in-built processing provided with the units software: Datalogx2. The data have been collected in the framework of the long term monitoring of the Western Channel Observatory stations and the Plymouth inshore fisheries undertaken annually by the Marine Biological Association of the United Kingdom. The RV MBA Sepia department of the Institute carried out the data collection activities.

  • The data set comprises more than 7000 time series of ocean currents from moored instruments. The records contain horizontal current speed and direction and often concurrent temperature data. They may also contain vertical velocities, pressure and conductivity data. The majority of data originate from the continental shelf seas around the British Isles (for example, the North Sea, Irish Sea, Celtic Sea) and the North Atlantic. Measurements are also available for the South Atlantic, Indian, Arctic and Southern Oceans and the Mediterranean Sea. Data collection commenced in 1967 and is currently ongoing. Sampling intervals normally vary between 5 and 60 minutes. Current meter deployments are typically 2-8 weeks duration in shelf areas but up to 6-12 months in the open ocean. About 25 per cent of the data come from water depths of greater than 200m. The data are processed and stored by the British Oceanographic Data Centre (BODC) and a computerised inventory is available online. Data are quality controlled prior to loading to the databank. Data cycles are visually inspected by means of a sophisticated screening software package. Data from current meters on the same mooring or adjacent moorings can be overplotted and the data can also be displayed as time series or scatter plots. Series header information accompanying the data is checked and documentation compiled detailing data collection and processing methods.

  • The North Atlantic Norwegian Sea Exchange (NANSEN) data set comprises hydrographic profiles (temperature and salinity) and time series of current velocity, temperature and occasionally conductivity from the North Atlantic Ocean. The measurements were collected between 1986 and 1988 using conductivity-temperature-depth (CTD) profilers, moored current meters and thermistor chains. Data collection was undertaken by six laboratories in four countries (Faroes, Germany, Norway and the UK). The NANSEN project was conceived by the International Council for the Exploration of the Sea (ICES) Oceanic Hydrography Working Group. It aimed to study the hydrography and circulation of the Iceland Basin and the temporal and spatial variability of the inflows and outflows across the Greenland-Scotland Ridge. Current meter data from a number of laboratories involved in NANSEN and CTD data collected by UK participants are managed by the British Oceanographic Data Centre (BODC). A further 50 current meter series have been collected, but have not yet been acquired by BODC. The data will be subjected to the usual BODC quality control procedures for current meter series. The hydrographic data set collected during the NANSEN experiment has been compiled by the ICES Secretariat.

  • The dataset comprises 6 hydrographic data profiles, collected by a conductivity-temperature-depth (CTD) sensor package, from across the Irish Sea and St. George's Channel, Bristol Channel and the Celtic Sea areas including specifically the Nymphe Bank and on the shelf edge in the vicinity of the Goban Spur. The data were collected during April of 1979. A complete list of all data parameters are described by the SeaDataNet Parameter Discovery Vocabulary (PDV) keywords assigned in this metadata record. The data were collected by the Institute of Oceanographic Sciences Wormley Laboratory.

  • The MeRMEED project aimed to determine and quantify how the interaction between mesoscale eddies and the steep slope along ocean western boundaries affects the dissispation of mesoscale eddies in these regions. The project comprised of a multi-platfrom programme involving ship-based and mooring-based obverations, including autonomous gliders, vertical microstructure profilers, CTDs and ADCPs. The MeRMEED project was run between 2015-2019, and focussed on the slope offshore of Great Abaco, Bahamas. The data contained in this dataset includes the data associated with three MeRMEED research expeditions aboard the R/V Walton Smith from 2016-12-01 to 2018-03-16. The data includes vertical microstructure profiler (VMP) measurements of the turbulent dissipation rate and temperature variance, profiles of temperature and conductivity from a CTD sensor attached to the VMP, and along-track meridional and zonal velocity profiles from a vessel mounted 75 kHz ADCP. Also included are two 75 KHz ADCPs mounted on the existing RAPID/MOCHA Western Boundary 1 mooring. The project was run by Eleanor Frajka-Williams (project PI) and Dafydd Gwyn Evans (post-doc) and funded by NERC Discovery Science grant NE/N001745/1.

  • The data set comprises acoustic and associated environmental data from multi-parameter underwater acoustic experiments undertaken in the Gulf of Lions, N.W. Mediterranean and Loch Ness, Scotland. Measurements were made over the period 30 January 1995 to 22 September 1995. Of primary interest were shallow water (10-200m), medium range (1-10km) channels at communication frequencies in the 10-100kHz range. Modulation techniques used include: Carrier Wave, ASK, PSK, FSK, Multi-ASK, Multi-PSK and Multi-FSK. Multi-parameter underwater acoustic experiments were carried out under high level control and in total more than 36 Gigabytes of acoustic and associated environmental data were gathered. Experiments were carried out at medium depth (50-100m) in the Gulf of Lions and deeper water (50-200m) in Loch Ness, and the data were stored on a series of CD-ROMs. A suite of tests was performed over set ranges (1km, 7km, etc.). In general, each range was contained on a set of three CD-ROMs which specifically referred to individual parameters set for that particular range (e.g. location, gain levels, projector and hydrophone depths). Alongside the data recordings, the IRIG 'B' time signal was also recorded during all experiments to allow derivation of precise timings of all signal transmissions and receptions. This information is also contained on the CD-ROMs. Associated environmental parameters were recorded and documented. These data were collected using CTD profilers, thermistor chains, tide gauges, current flow meters and an ORETECH Weatherpak-400. The raw data were logged in an ASCII format on a DAT cartridge. The primary aim of EEVMAC (European Experimentally Validated Models for Acoustic Channels) was the generation of signals and the recording of data for propagation model validation in connection with the characterisation of underwater acoustic channels. Data were collected by researchers from Heriot-Watt University, UK and the Laboratoire de Physique et Chimie Marines (LPCM), France. The British Oceanographic Data Centre holds 19 Gigabytes of edited data on CD-ROM, along with copies of the raw environmental data. Further details on the environmental data can be sought from Laboratoire d’Oceanographie de Villefranche, formerly LPCM.

  • The data set comprises continuous hourly recordings of electrical potential across the Dover Strait, which relate to the flux of water, over the period 1955-1965 and part of 1968-1969, together with parallel measurements of sea temperature and pressure. Voltages on telegraph cables were measured almost continuously by pen recording milliammeters installed at Dover since 1954. The d.c. potential between the inner conductor of the cable and its screen is measured through a 2.2 kohm resistor in series with a milliammeter, whose internal resistance was of order 1 kohm. The screen was earthed at both the English and French ends, and at the French end the conductor is also effectively earthed (through inductive elements) as far as low frequency voltage variations were concerned. Thus the voltage recorded at St. Margaret's Bay is effectively the difference in earth potentials between the particular coastal points in England and France. A 0.003F capacitance in parallel with the milliammeter shunted out voltage variations with time scales less than about half a minute. For calibration, a standard voltage cell was switched in place of the cable on occasions. For parallel measurements of sea temperature (related to conductivity) and local wind conditions, 6-hourly temperatures and barometric pressures from the Noord Hinder Light Vessel, the pressures from the Terschellinger Bank Light Vessel and the 6-hourly pressures from Gorlston (East Anglia) were used. Data for sea salinity at the Varne Light Vessel were extracted from International Council for the Exploration of the Sea (ICES) publications.

  • The dataset comprises 36 hydrographic data profiles, collected by a conductivity-temperature-depth (CTD) sensor package, from across the Irish Sea and St. George's Channel, and the North East Atlantic Ocean (limit 40W) areas specifically from around the Rosemary Bank and George Bligh Bank areas. The data were collected during August and September 1978. A complete list of all data parameters are described by the SeaDataNet Parameter Discovery Vocabulary (PDV) keywords assigned in this metadata record. The data were collected by the Institute of Oceanographic Sciences Wormley Laboratory.

  • A dataset collected by investigators of the University of East Anglia during January - February 2020 in the tropical North Atlantic. Gliders SG620 and SG637 were deployed from the RV Meteor during cruise M161 as part of the EUREC4A oberservational campaign. Glider SG579 was deployed by the autonomous surface vehicle Caravela. All gliders were recovered by the Meteor. SG620 and SG637 occupied a bowtie pattern 10 km across centered at 14'10''N 57'20''W. The two gliders were deployed with CT sails measuring conductivity and temperature and completed 131 and 155 dives respectively. SG579 was deployed at 13'21''N 58'50''W and travelled 200 km to the bowtie over 10 days conducting 75 dives. Once onsite, SG579 conducted a further 220 dives. In addition to a CT sail, SG579 carried a PAR sensor and Wetlabs sensor measuring backscatter, chlorophyll a and CDOM. Data were processed using the UEA Seaglider Toolbox.