The Santa Monica Basin tracer experiment: Comparison of release methods and performance of perfluorodecalin and sulfur hexafluoride

Watson, Andrew; Ledwell, James R.; Sutherland, Stewart C

doi:10.1029/91jc00105

Cited by 22 publications

(10 citation statements)

References 12 publications

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“…In the concentration range of 0.4 to 500 pmol • L -1 (1 pmol = 10 -12 mol) SF 6 can be detected by gas chromatography combined with an electron capture detector (ECD) without previous extraction or dilution step (Schlatter, 1991;Watson et al, 1991). For the gas chromatographic analysis, 25 mL of water is drawn into a 50 mL glass syringe filled with 25 mL of N 2 (details in Schlatter et al, 1990).…”

Section: Tracer Techniquementioning

confidence: 99%

Hypolimnetic density currents traced by sulphur hexafluoride (SF

Schlatter¹,

Wüest²,

Imboden³

1997

Aquat. Sci.

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The artificial tracer sulphur hexafluoride (SF 6 ) has been used to study the density-driven deep water exchange between two sill-separated basins of Lake Lucerne, Gersauersee and Urnersee. The sources of the density gradients between the two basins are (1) salinity differences between the major inlets due to the different geology of their drainage areas, and (2) temperature differences due to spatial variation of wind forcing. Wind speeds are generally larger in Urnersee, especially in spring during the so-called Föhn events, when winds blow from the south. In contrast, Gersauersee is protected form these winds. In spring 1989, a total of 630 g of SF 6 was released at 80 to 120 m depth in the small Treib Basin located between Urnersee and Gersauersee. During about 100 days the distribution of SF 6 in the lake was determined by gaschromatography. Two models are used to quantify the exchange flow, (1) a one-box mass balance model for SF 6 in the deep part of Treib Basin, and (2) a one-dimensional diffusion/advection model describing the temporal and vertical temperature variation in Urnersee. According to the first model, the flow into the deep hypolimnion of Urnersee, decreases from 21 • 10 6 m 3 • d -1 at the end of March to about 8 • 10 6 m 3 • d -1 in late April. The second model yields similar flow rates. The decrease of the flow rate during spring, confirmed by both approaches, is consistent (1) with the decreasing strength of the density gradient above the sill during spring and early summer, and (2) with hydrographic information collected in Lake Lucerne during other years.

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Section: Tracer Techniquementioning

confidence: 99%

Hypolimnetic density currents traced by sulphur hexafluoride (SF

Schlatter¹,

Wüest²,

Imboden³

1997

Aquat. Sci.

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“…They determined a vertical diffusion coefficient (across the density gradient) of approximately 0.25 cm 2/s while lateral mixing across the basin required on the order of months. In a paper on the same experiment, Watson et al 90 compared the performance of the two tracers, perfluorodecalin and sulfur hexafluoride, and their associated release methods. McDouga1l 9 1 presented a method in which the distributions of salinity, temperature, and a third conservative variable can be used to distinguish lateral June 1992 Fate and Effects of Pollutants and vertical mixing.…”

Section: Coastal and Oceanicmentioning

confidence: 99%

Mixing and transport

Shanahan¹

1992

Water Environment Research

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“…Upstill-Goddard et al 1990). We automated the analysis and applied it to a continuously pumped seawater stream in a manner similar to that described by Watson et al (1987). Two cryotraps were used alternately; while one was in the purge line being charged with volatiles from the seawater, the other was being heated, desorbed, and its contents analyzed.…”

Section: Tracer Releases In the North Seamentioning

confidence: 99%

Design of a small-scale in situ iron fertilization experiment

1991

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We consider the design of an in situ enrichment experiment to test the hypothesis that Fe deficiency limits primary productivity in some regions of the ocean. A small-scale (1 O-l 00 km2) experiment would be preferable for logistical reasons, but the chief practical difficulty is that the patch of enriched water will fragment or streak severely. This problem is made tractable by adding a conservative marker such as sulfur hexafluoride (SF,) along with the Fe release, enabling rapid detection of enriched water despite fragmentation. The concentration of SF, would indicate the amount of dilution the original injection of Fe had undergone, and regression of parameters such as pC0, and Chl against SF, at several times postinjection would enable the degree of fertilization to be assessed. Due to the complexity of Fe chemistry in seawater, we cannot be certain that the added Fe will adequately mimic the input of natural aerosol Fe to the surface. Thus, a null result from the experiment (i.e. no observable fertilization) would be less valuable than a positive result: a positive outcome would be proof that Fe enrichment enhances productivity, but a null result would not be absolute proof of the converse.

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The Santa Monica Basin tracer experiment: Comparison of release methods and performance of perfluorodecalin and sulfur hexafluoride

Cited by 22 publications

References 12 publications

Hypolimnetic density currents traced by sulphur hexafluoride (SF

Hypolimnetic density currents traced by sulphur hexafluoride (SF

Mixing and transport

Design of a small-scale in situ iron fertilization experiment

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