Hydrographic Measurements

A NOAA/PMEL-designed, 36-position, 10-L rosette frame was used at 84 of the 88 stations during the expedition. A smaller 12-position, 2.4-L rosette was used as a bad-weather backup system at several stations during the cruise. A General Oceanics (GO) 36 "Intelligent" underwater array (pylon) and deck unit was used with the PMEL 36-position system, along with a Neil Brown Instrument Systems (NBIS) MARK III CTD (serial # 1111). The CTD pressure, temperature, and conductivity data were processed and corrected according to laboratory calibrations. Pressure values are expected to be accurate to ±3 dbar, temperature values to ±0.002°C.

The salinity analysis aboard R/V John V. Vickers was determined exclusively with a Guildline 8400 Autosal. This instrument was located in a temperature-controlled room at 20.5 ± 1°C. The bath of the autosal was kept at 21°C and proved to be very stable throughout the cruise. Standardization of the autosal was carried out with International Association for the Physical Sciences of the Ocean (IAPSO) Standard Seawater batch P114.

Samples of dissolved oxygen were collected soon after the rosette sampler was brought on board and after CFC and helium samples were collected. Calibrated 125-mL nominal volume iodine determination flasks (Corning 5400-125) were used for sampling. Titration was performed by Carpenter's (1965) whole bottle technique with a modification of the system described by Friederich et al. (1991).

All analyses for nutrients were done with an Alpkem RFA/2 320 autoanalyzer. The methods used were modified from those recommended by the Alpkem Corporation. The working nutrient standards used were a mixture of phosphate, silica, nitrate, and nitrite in a low-nutrient natural seawater matrix. Simultaneous analyses were run on the RFA/2 for all of these nutrients.

For more detailed information on hydrographic measurements, please see the Chief Scientist report at http://whpo.ucsd.edu/data/onetime/pacific/p13/p13/index.htm.


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