Brief Cruise Summary

R/V Thomas Washington departed Papeete, Tahiti, for its third consecutive WOCE leg on August 31, 1991. Stations were numbered consecutively from the beginning of the R/V Thomas Washington work on Leg 1 (TUNES-1 Expedition, WOCE Section P17C), starting off the coast of California in May 1991. The first station 221 on Leg 3 was occupied on September 1, 1991, at ~17° 31´ S and 150° 29´ W and was a reoccupation of the last station 220 on Leg 2 (TUNES-2 Expedition, WOCE Sections P17S and P16S). The last station of the TUNES-3 Expedition was occupied on September 30, 1991, at 18° 53´ N and 155° 39´ W. On October 1, 1991, R/V Thomas Washington arrived in Honolulu, Hawaii.

During the 31-day expedition, 105 hydrographic and 8 large-volume stations were completed. All stations were sampled to the bottom and consisted of a rosette/CTD cast. Basic station spacing was 30 nm, closing to 10 nm between 3° S and 3° N. Sampling was performed with a 36-place, double-ring rosette with mounted CTD (WHOI CTD 10) and transmissometer. CTD data consisted of pressure, temperature, conductivity, oxygen, and transmissometry. Water samples were collected for analyses of salt, oxygen, silicate, phosphate, nitrate, and nitrite on all stations and CFC-11, CFC-12, ³H, tritium, ¹⁴C, TCO₂, and TALK on selected stations. Underway measurements included ADCP, surface temperature, and surface water partial pressure of CO₂ and N₂O.