Olaf Klatt

A Profiling Float’s Sense of Ice

Abstract The Argo project intends to continuously monitor temperature and salinity of the upper 2000 m of the global ocean by use of autonomous, vertically profiling floats. They are currently generating the largest oceanographic dataset that ever existed, covering most of the world’s oceans. However, the use of these instruments in the polar oceans is seriously impeded by the presence of sea ice, as floats are hindered from transmitting their profile data or, even more seriously, potentially damaged when ascending to, or being at, the ice-covered sea surface. The authors present a cost neutral ice sensing algorithm (ISA), which alerts for the likely presence of sea ice. In this event, the profile is aborted and no surfacing attempted. To retrospectively track floats that actively remained under the sea ice because of ISA, acoustic tracking via the RAFOS technique was tested in the Weddell Sea. Last but not least, the most recent version of floats features the option of interim storage of profiles that co...

A capillary‐column chromatographic system for efficient chlorofluorocarbon measurement in ocean waters

We describe a new gas chromatographic analytical system for the joint measurement of the chlorofluorocarbons CFC-1 1, CFC-12, and CFC-113 and of CCl 4 in ocean waters. From measurements at sea and in the laboratory we find overall precisions for surface waters of±0.6, 0.6, 1.5, and 2.4% and detection limits of 0.002, 0.002, 0.008, and 0.003 pmol/kg, for CFC-12, CFC-11, CFC-113, and CCl 4 , respectively (1-σ equivalents). The measurement repeat period is 17 min. A purge-and-trap approach, and other details, pay tribute to the work of Bullister and Weiss [1988]. A capillary column in combination with a low-volume trap yields higher resolution than reported for other systems. There is full separation of CFC-12 from N 2 O and a satisfactory one of CFC-113 from CH 3 I; to achieve the latter, a short packed column is operated in series with the main column. Slow purging of CCl 4 from the water samples contributes to its analytical error. The system is fully automated, allowing eight water samples and associated calibration measurements to be carried out unattented. Water samples are transferred into the system by means of flow-through containers incorporating glass ampoules. Alternatively, the ampoules can be flame-sealed, allowing sample storage for later analysis ashore. The performance of the system is assessed in some detail to serve as reference information for other CFC measurement systems and to direct future system tuning and developments. The system has been successfully employed at sea repeatedly. Sections from cruise M30/2, 1994 (Atlantic, 48° N), are presented as an example.

Bottom water circulation in the western equatorial Pacific as inferred from carbon tetrachloride observations

Hydrographic and tracer data from the western equatorial Pacific, collected during cruise 113 of R/V Sonne in October–November 1996, are discussed in the context of spreading of lower Circumpolar Deep Water (lCDW). The horizontal distribution of CCl4 and other properties indicate a deep western boundary current north of the Caroline Seamounts. Elevated concentrations of CCl4 at the bottom show that a small fraction of lCDW in this region is younger than about 70 years. This age is used to infer a minimum spreading rate of about 0.8 cm/s for the young components of this water mass. The current appears to bifurcate at about 143°E into topographically guided northward and westward currents.