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  • 1
    Electronic Resource
    Electronic Resource
    A SF6 tracer study of horizontal mixing in Lake Constance (1994)
    Springer
    Aquatic sciences 56 (1994), S. 307-328 
    Details
    ISSN: 1420-9055
    Keywords: Horizontal mixing ; Lake Constance ; tracer experiment ; sulfur hexafluoride ; integrating sampler
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Horizontal mixing processes in the hypolimnion of the western part of Lake Constance are studied by measuring the dispersion of a sulfur hexafluoride (SF6) tracer plume. Only 1 liter gaseous SF6 (STP) was released at a central hypolimnic depth of 60 m in August 1990. Over a period of 3 months the horizontal dispersion of the tracer plume was measured by 19 surveys using a new, vertically integrating sampling device. The observed horizontal dispersion is marked by strong storm-induced stirring events. Nevertheless mean turbulent diffusion coefficients for the whole period can be computed. They rise about linear from 0.7 ⋅ 105 cm2/s to 3.0 ⋅ 105 cm2/s with the distance from the western end of the lake. For the hypolimnion of Überlingersee, a sill-separated basin in the western part of Lake Constance, a simple budget model gives an exchange time of 67 ± 6 days with the main basin (Obersee).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877179
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Vertical mixing in Überlingersee (Lake Constance) traced by SF6 and heat (1994)
    Springer
    Aquatic sciences 56 (1994), S. 329-347 
    Details
    ISSN: 1420-9055
    Keywords: Vertical mixing ; Lake Constance ; tracer experiment ; sulfur hexafluoride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vertical mixing in Überlingersee is studied by releasing sulfur hexafluoride (SF6) as a tracer at a central hypolimnic depth of 60 m and measuring its subsequent vertical dispersion over a period of three months. The experiment started with a streaky tracer injection of 1 liter gaseous SF6 (STP) in August 1990. At that time the lake showed a typical strong summer stratification which in a weakened form lasts until November. From the SF6 profiles of fifteen surveys at three sampling sites vertical diffusivitiesK z are calculated compensating internal seiche displacement and horizontal tracer loss. Except of the bottom region no sampling site or time period is marked by significant differences in the hypolimnicK z profile. So vertical mixing in the whole Überlingersee is described by mean diffusivities decreasing from 1.7 cm2/s at 120 m depth to 0.4 cm2/s in 30 m. The minimal value of 0.3 cm2/s in the thermocline region at 20 m depth is only based on observations in autumn. For a strong summer stratification it is certainly lower. The gradient-flux-method for heat was applied to compute a meanK z (T) profile from continuously measured temperature profiles. Significant differences resulting from the two tracers showed, that theK z (T) values are underestimated by up to a factor of 5 if cooling by lateral exchange is neglected. Particularly, internal seiche pumping of colder water from the adjacent Lake Obersee over the separating sill of Mainau into the deep Überlingersee basin is observed in 1990 from August onward, obviously controlling the heat budget below the sill level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877180
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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