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Physical oceanography at CTD station DI191_12079#3

Publication Date
DOI: 10.1594/pangaea.196071
  • 12079#3
  • Biogeochemical Ocean Flux Study
  • Bofs
  • Calculated
  • Ctd
  • Neil Brown
  • Mark Iii B
  • Ctd/Rosette
  • D191
  • Density
  • Sigma-Theta (0)
  • Di191_12079#3
  • Discovery (1962)
  • Fluorescence
  • Chlorophyll
  • Irradiance
  • Downward Par
  • Jgofs
  • Joint Global Ocean Flux Study
  • Optical Beam Attenuation Coefficient
  • 660 Nm
  • Pressure
  • Water
  • Salinity
  • Temperature
  • Water
  • Transmissometer
  • Sea-Tech 25 Beamlength
  • 660 Nm
  • Uv Aquatracka Fluorometer
  • Chelsea Instruments


CTD Data for Cruise Discovery 191 (11 May - 5 June 1990) 1) INSTRUMENTATION The CTD profiles were taken with an RVS Neil Brown Systems Mk3B CTD incorporating a pressure sensor, conductivity cell, and platinum resistance thermometer and a Beckmann dissolved oxygen sensor. During the first cast, the oxygen sensor failed and salinity exhibited an alarming positive drift. This was due to leakage through the oxygen sensor which was removed and replaced by a blanking cap. As a precaution against further leakage, this instrument (termed the RVS CTD in this document) was restricted to depths of 300m or less. For deeper casts, a backup CTD unit loaned by IOSDL was used (termed the IOS CTD in this document). This was a Neil Brown Mk3 unit with no oxygen sensor and no connections for an external fluorometer or transmissometer. The CTD unit was mounted vertically in the centre of a protective cage approximately 1.5m square. Where fitted, a Chelsea Instruments Aquatracka fluorometer, and a SeaTech red light (661nm) transmissometer with a 25cm path length were attached to the bars of the frame. Above the frame was a General Oceanics rosette sampler fitted with 12, 10 litre Niskin bottles. The bases of the bottles were 0.75m above the pressure head with their tops 1.55m above it. One of the bottles was fitted with a holder for up to three digital reversing thermometers mounted 1.38m above the CTD temperature sensor. On deep casts, a second bottle was sometimes similarly equipped. Above the rosette was a PML 2-pi PAR (photosynthetically available radiation) sensor pointing upwards to measure downwelling irradiance. A second such sensor was fitted to the bottom of the cage facing downwards to measure upwelling irradiance. It should be noted that the PAR meters were vertically separated by approximately 2m. These instruments were only attached for casts of 300m or shallower. Lowering rates of up to 1.5 m/sec were used, although rates were generally in the range 0.5 - 1 m/sec. Bottle samples and reve

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