Cruise Summary

The BNL CO₂ group, consisting of K. M. Johnson and R. Ramirez, arrived in Reykjavik, Iceland, on August 29 and went aboard the next day to join the IFMH CO₂ group members, Drs. Bernd Schneider and Lutger Mintrop. Dr. Jens Meincke was already aboard as Chief Scientist. Setting up of the equipment began on August 30 and was completed on the morning of September 2. The R/V Meteor departed Reykjavik at 11 a.m. on September 2, 1991. The ship immediately encountered rough weather conditions with gale force winds. Two test stations were completed during the transit across the Denmark Strait to the first station (no. 558) on the South-East Greenland shelf, which was reached on September 5. The earlier gale force winds were replaced by a quiet period characterized by humid air masses over cold water, which resulted in fog. The hydrocast routine was interrupted by winch and rosette bottle-release problems on September 6 and 7 and by currentmeter deployments on September 9, 10 ,11, 14, and 19. Bad weather forced several delays on September 13, when the pressure dropped to 980 hPa, wind gusted to 11 Beaufort, and waves rose to 8 m. This scenario was repeated on September 17, and the slowly receding sea conditions thereafter continued to plague the oceanographic work until the end of the hydrographic program of WOCE section A1E at station 622 on September 21. Each rough period was followed by reduced sampling on stations (12 bottles instead of 24 on each rosette), but these stations were restricted to short lines perpendicular to the WOCE line. The station locations are shown in Fig. 1. Of the six stations (592, 593, 595, 606, 607, and 608) taken normal to the WOCE line, only station 607 was sampled for carbonate system parameters. XBT measurements were made at selected CTD stations in parallel with the CTD casts, and acoustic Doppler current profiles (ADCP) were made continuously from September 2 to September 22 to measure the instantaneous near-surface currents.

Two single-operator multiparameter metabolic analyzers (SOMMAs) from BNL (hereafter the systems are designated BNL I and BNL II), one potentiometric alkalinity titrator from IFMK and one ifrared-based system for underway pCO₂ measurements from IFMK, were on board for this cruise. A total of 583 TCO₂ samples, normally collected in conjunction with tracer samples, were taken from 31 section stations, 1 test station (no. 557) and two calibration stations (nos. 581, 608) from a total of 59 bottle casts. Not all 59 stations could be sampled for tracers and TCO₂ because of the limited time available for analysis. The standard WOCE parameters (oxygen, nutrients, and salinity) were sampled on all stations, and on approximately every other station these were augmented by the tracer samples for CFCs, carbonate, helium, tritium, and radiocarbon as the ship steamed eastward from the southeastern tip of Greenland to the coast of Ireland. The density of the CO₂ sampling was fairly constant, ~2 stations per day; the underway pCO₂ system operated continuously.

Both electrical and mechanical problems were noted for each of the SOMMA coulometer systems. BNL II was most severely affected and was declared nonoperational on September 16, when the magnetic valves on the SOMMA chassis could no longer be operated reliably, the electronic calibration factor suddenly changed by +0.11% (a factor of 10 higher than the usual precision of ± 0.01%), and the communication between the keyboard and PC became erratic. The final Certified Reference Material (CRM) run on this date was 6 µ mol/kg lower than the certified value, and test sample duplication was equally poor. When this system was operated several months later in the laboratory, all components functioned satisfactorily, and it was impossible to determine the cause of the shipboard difficulties. BNL I experienced two serious problems. First, the BNL I coulometer became inoperable when the photodetector amplifier failed on September 7. Fortunately, a backup coulometer from Kiel was available, and it was immediately placed in service. Second, the gas calibration system apparently failed on September 10 as a result of cross-talk between the gas sample loops (CO₂ leaking from one loop into the other through a surface scratch or scoring of the valve, which contaminates the carrier gas). This manifested itself as a very noisy system with a very high and unusable blank. The problem was corrected by disconnecting the gas sample valve from the system so that the carrier gas (N₂) passed directly from the gas cylinder into the SOMMA stripper.

Because of the rough weather, plans for a return voyage around the north of Scotland to Hamburg were changed, and the ship arrived in Hamburg on September 25, via the English Channel, where winds astern arising from a low pressure system near the Faeroe Islands hastened the return voyage.