Gerold Siedler relieved Walter Zenk as chief scientist upon completion of the R/V Meteor Cruise 15/2 on February 8, 1991, in Vitoria, Brazil; the remaining participants were on board by February 9. Equipment setup began on February 8. The R/V Meteor departed Vitoria at 9 am on February 10, 1991, and steamed to its initial position of 19oS, 38oW. On February 11 the ship began a short zonal section across the Brazil Current characterized by closely spaced expendable bathythermograph (XBT) launches and acoustic Doppler current profiling (ADCP). A test station was made to check CTD operation and possible contamination of the 10-liter Niskin bottles for CFCs. From these results and the earlier profiles, a decision was made to run westward to the 500-m isobath where the Section A9 began with a set of eight closely spaced expendable current profiler (XCP) and CTD profiles including the standard measurements (nutrients, O2, CO2, tracers) as the ship steamed once again eastward across the Brazil Current and into the open ocean along 19oS. Neither tracer nor CO2 samples could be taken on all CTD stations because of the time required for analysis. The density of the CO2 sampling was gradually increased during the first week until at least one CO2 station was completed each day (Fig. 1). Initial delays were aggravated by high (+ 3 to 10 µ mol/kg) TCO2 results for the certified reference material (CRM) analyses with respect to the certified value. It was initially assumed that the problem lay with the SOMMA-Coulometer system or its software, and time was lost troubleshooting. After analyzing a limited number of samples from an earlier CRM batch over several days, it was found that the measurement system was operating properly and that the new CRM batch supplied especially for the cruise was at fault. This was confirmed by subsequent testing.
To compare these data with data from the earlier U.S. South Atlantic Ventilation Experiment (SAVE) Program, the normal station routine (i.e., every 30 nm) was interrupted at 25oW between February 19 and 20 for an additional three stations north and south of 19oS. To identify deep water movements on the western edge of the Mid-Atlantic Ridge, between February 25 and 27 a short meridional section comprising seven stations was carried out from 19o00'S to 23o40'S. Between March 3 and 6 the ship veered slightly southward to avoid the 200-mile commerce zone belonging to the island of St. Helena (United Kingdom). Between March 12 and 15 a diversion was made at 7oE to the Walvis Ridge, and eight CTD stations were taken along a track parallel to the ridge to study deep water movements in this region. The ship continued the zonal section along 19oS until ~8oE where a course change to east-northeast was made. To adequately sample the eastern boundary current up to the continental shelf, the distance between stations at this point was reduced from 30 to 10 nm. On March 19, 1991 WOCE Zonal Section A9 was completed. The ship steamed to Pointe-Noire, Congo, arriving on March 23, 1991. Weather and sea conditions were excellent throughout the cruise.
akozyr 9/05/96
