Nella Dan: FIBEX Cruise - Oceanographic and nutrient data
Oceanography and nutrient measurements were taken where possible, which was not always at ideal locations. Therefore coverage of the area is not necessarily complete. Nutrient data were only recorded at 14 out of the 52 CTD stations. This cruise is however part of a series of 6 cruises which operate...
| Summary: | Oceanography and nutrient measurements were taken where possible, which was not always at ideal locations. Therefore coverage of the area is not necessarily complete. Nutrient data were only recorded at 14 out of the 52 CTD stations. This cruise is however part of a series of 6 cruises which operated in this area, providing data from varying seasons and condition. Data collection: Continuous vertical profiles of conductivity and temperature were obtained using a Neil Brown Mark III CTD (conductivity, temperature and depth probe #2568) system, attached to a rosette water sampler (InterOcean). The temperature sensor was a platinum resistance thermometer with a range of -3 to 32 degrees celcius, the conductivity sensor had a range of 1-65mmhos, and the pressure sensor had a depth range of 0-3200dbar. For the nutrient data, water samples were collected using the rosette sampler and 5 L Niskin bottles. Two stations were made per day, one close to solar noon and the other at solar midnight. The depth of each cast was usually to 2000m or to near bottom if shallower. Measurements were made on the downcast and samples collected on the upcast. The CTD was lowered at a rate as close as possible to 1m/sec. The CTD was raised at speeds between 1m/s and 2m/s between sampling. At water sampling stations, conductivity and temperature was recorded. Output from the temperature, conductivity and pressure depth sensors were transmitted as a data set to the deck unit at 30 data sets per second. Data was initially recorded on audio cassettes. Ship-board processing: Oceanographic analysis - water samples were analysed for salinity and oxygen. Nutrient analysis-250mL water ' sub-samples were filtered through GF/F glass fibre filters, transferred to Whirlpacks and immediately frozen. Post-ship processing: Oceanography data - Data was initially recorded on audio cassettes, but later replayed to produce digital nine-track magnetic tapes by a PDP 11/23. Data tapes were then processed on a VAX 11/750. For each CTD downcast, an uncalibrated, despiked file was generated, using a recursive filter to compensate for sensor mismatch. The data files were used to generate 2 dbar averages for in situ temperature, salinity, sigma-t, specific volume anomaly and geopotential anomaly. The averages were centred on even, integral depths, and were only calculated when averages contained eight or more valid data points. The temperature and conductivity means were calculated for the interval, and the salinity calculated for the mid point of the pressure interval from the temperature and salinity means. Data processing software was supplied by CSIRO Division of Oceanography. Nutrient data - Analyses was completed by the Australian Government Analytical Laboratories for nitrate, nitrite, silicate, phosphate, chlorophyll a and other pigments. The complete dataset is logically consistent, as krill and zooplankton hauls and phytoplankton pigment analysis were also obtained at the same sampling sites as the oceanographic and nutrient data. The cruise track was established before the experiment in order to eliminate bias. The oceanographic sampling was done as a supplement to the krill research program and the nutrient sampling to help interpret phytoplankton distribution and abundance, so sampling location and depth were not necessarily selected according to oceanographic or nutrient related considerations. This dataset contains CTD (conductivity, temperature, depth) and nutrient (nitrate, phosphate, silicate) data obtained from the First International BIOMASS Experiment (FIBEX) cruise of the Nella Dan, during Jan - Mar 1981. The cruise is the first in a series of six, providing a long term field survey studying krill and other zooplankton. 52 CTD casts were taken in the Prydz Bay region, and nutrient data were collected at 14 out of the 52 CTD stations. Casts were made to 2000 m or to near bottom if shallower. The oceanographic sampling was done as a supplement to the krill research program and the nutrient sampling to help interpret phytoplankton distribution and abundance, so sampling location and depth were not necessarily selected according to oceanographic or nutrient related considerations. |
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