3.2 WOCE Section P17E/P19S

R/V Knorr departed Papeete, Tahiti, on December 4, 1992, and headed toward the first station of the WOCE Section P17E/P19S (see Fig. 1). On the afternoons of December 5, 6, and 7, the vessel stopped for station tests and training. No reportable data were collected. WOCE stations began at 52.5°S, 135.0°W on December 13 (local time) and continued on the planned track until the Antarctic ice edge was reached at 66.3°S, 126°W on December 25. After a 3-day run north to 52°S, 125.3°W, WOCE P17E stations resumed on December 29 along a track slightly south of the originally planned line, ending at 54°S, 88°W on January 9. At this point the track turned south to follow the originally planned P19S line south to 69.3°S, 88°W when station work was terminated short of the ice edge because of the need to begin the run into port. However, the track exceeded the planned minimum southward goal of 67°S, which was the latitude of the R/V Akademik Ioffe crossing of the S4P line. The R/V Knorr arrived in port on schedule January 22, 1993. The total number of stations was slightly less than planned, but a preliminary examination of the isopleths suggests no serious data loss was generated by the use of 40-nm spacing over three "deep basin" portions of the expedition.

The principal sampling program consisted of full-depth CTD profiles with a maximum of 36 small-volume water samples per cast. Water samples were collected for salinity, dissolved oxygen, silicate, phosphate, nitrate, and nitrite from all sampled levels at all stations and for CFC- 11, CFC-12, CFC-113, CCl₄, ³He, tritium, ¹⁴C, and CO₂ system parameters at selected levels and stations. Large-volume sampling for ¹⁴C was carried out at 7 stations with 270-L Gerard barrels, with up to 18 samples per station in 2 casts. Check samples for salinity and silicate were analyzed from the Gerard barrels and their piggyback Niskin bottles. Separate surface-water samples were taken approximately one each day for analyses of ²²⁶Ra and ²²⁸Ra. Separate surface samples were filtered at each station for shore analyses of ¹³C in dissolved CO₂.

Rosette water samples were collected by the SIO Oceanographic Data Facility (ODF) from ODF-constructed 10-L sample bottles mounted on an ODF-constructed 36-bottle rosette sampler that used General Oceanics 24- and 12-place pylons. The rosette was equipped with an ODF-modified Neil Brown Instrument Systems (NBIS) Mark IIIb CTD for in-situ measurement of conductivity, temperature, pressure, and dissolved oxygen. A transmissometer belonging to Dr. Wilf Gardner, TAMU, was installed on the rosette and used at every station. A short-range (100 m) altimeter was mounted on the rosette frame and its data fed into the CTD data stream. A pinger on the rosette frame gave height-above-bottom throughout the water column. In every case the bottles were closed at selected depths during the up cast, after the winch had stopped at that depth. There were 106 CTD/rosette stations, each close to the bottom. Seven included one deep and one intermediate depth cast with Gerard barrels.

While on station and underway a shipboard ADCP system was operated. Underway surface measurements were also obtained for temperature, pCO₂, and atmospheric CFCs. Sonic depth and position were recorded at 5-minute intervals between most stations and along selected portions of the long runs. Routine weather observations were collected at 4-hour intervals by the ship's officers, and an Improved Meteorological (IMET) system was operated by the R/V Knorr's resident technician.

The sea work was occasionally affected by high seas and swells generated by low-pressure cells in the region.