Cruise Summary

On December 26, 1992, K. Johnson of BNL arrived in Rio de Janeiro, where he joined Drs. B. Schneider and L. Mintrop and their CO₂ group consisting of A. Morak, U. Karbach, A. Korves, and J. Morlang who were already onboard the R/V Meteor. Setting up of the equipment began immediately by locating the coulometry systems in the Universal Laboratory, the underway pCO₂ system in the Geo-Laboratory, and the alkalinity system in one of the ship's chemistry laboratories. The R/V Meteor departed Rio de Janeiro at 6 p.m. on December 27, 1992. Work began almost immediately with ADCP and XBT measurements across the Brazil Current and the occupation of test station no. 620 (waypoint A). Then R/V Meteor headed to waypoint B and once again crossed the Brazil Current, where additional ADCP and XBT measurements were made (Fig. 1). After R/V Meteor crossed the Brazil Current for the second time, the ship began the hydrographic stations at waypoint C. Between waypoints C and B the interval between stations was ~10 nm, and after waypoint B it rose to ~30 nm. The CO₂ sampling began at test station no. 620. The 30° S parallel was reached at waypoint D, and for the next few weeks the R/V Meteor sailed eastward along the 30° S parallel, passing over portions of the Vema Channel, the eastern part of the Rio Grande Rise, the Argentine Basin, the southern Brazil Basin, the Mid-Atlantic Ridge, the Angola Basin, the Walvis Ridge, and the Cape Basin. There was a small interruption in the work schedule to allow a New Year's Eve celebration. On January 8, nets laid by Spanish fishing boats on the western edge of the Rio Grande Rise caused the R/V Meteor to make a detour. (However, this meeting with the fishing boats also resulted in a trade between captains in which the R/V Meteor received fresh swordfish and tuna). A small northward jog was made over the Walvis Ridge in order to sample around topographical features. The intervals between stations as the ship steamed eastward varied between 9 and 45 nm to limit the difference between the bottom depth at consecutive station depths to 1000 m. At 11° 30' E, the ship veered slightly to the east-northeast in order to avoid the South African 200-nm exclusion zone because permission to sample in these waters had not been obtained. After this turn, the station resolution was reduced to 20 nm until the last station on the African shelf at a depth of ~200 m. The measurement phase concluded on January 28, 1993, and the R/V Meteor steamed to Capetown, where it arrived on the afternoon of January 30. Aside from some light rain and intermittent cloudiness at the beginning of the cruise, the weather remained mostly sunny with summer temperatures and calm seas throughout. Closer to the coast of Africa, swells of ~5 m originating from subantarctic low-pressure areas were experienced but without any loss of work time.

Two Single-Operator Multiparameter Metabolic Analyzers (SOMMAs) were used for measuring TCO₂ concentration during this cruise. One was supplied by BNL and another by the IfMK. In addition, two potentiometric alkalinity titrators from IfMK were run in parallel, and an infrared (IR)-based system for measuring underway pCO₂ belonging to IfMK was deployed. The TCO₂ concentration was analyzed in 1425 samples from 57 of 100 CTD stations (57%) occupied during the cruise Fig. 2. In addition, 116 coulometric measurements for the Certified Reference Material (CRM) and duplicate analyses were made during the cruise. The TALK concentration in 665 samples was determined by potentiometric titration during the cruise. Not all stations could be sampled for TCO₂ and TALK because of the time required for analysis; however, the goal of 50% station coverage for CO₂ samples was surpassed, and on average 1.5 stations were sampled per day by the CO₂ group. The standard WOCE parameters (oxygen, nutrients, and salinity) were analyzed on all samples, and the tracer samples included CFC's, helium, tritium, and radiocarbon. The underway pCO₂ system operated continuously.