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| Titel |
Vertical Mixing in the Dead Sea |
| VerfasserIn |
Isaac Gertman, Tal Ozer, Boris Katsenelson, Nadav Lensky |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250113929
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| Publikation (Nr.) |
 EGU/EGU2015-14173.pdf |
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| Zusammenfassung |
| For hundreds of years, the Dead Sea was characterized by a stable haline stratification, supported by runoff. The penetration of the winter convection was limited to an upper mixed layer (UML) of about 30--50 $m$. Below the UML, a stable halocline prevented the mixing. As a result of the runoff reduction, the UML salinity increased and the gravitational stability diminished. During the winter of 1978--1979, the sea water overturned, ending the long-term stable hydrological regime. Since 1979, the haline stratification structure reoccurred twice after extremely rainy winters, in 1980--82 and 1992--1995. In other years, the sea was entirely mixed by winter thermal convection ( which occurs from November to March ) and had a seasonal pycnocline beneath the UML during summer.
Profiles of temperature and quasi-salinity (density anomaly from $1000 \text{kg}/\text{m}^3$ for the chosen reference temperature of $32^\circ \,C$) during the last 19 years, show the formation of summer ``overturning halocline'' beneath the UML, and the thermocline that supports the stable stratification.
Another warm and saline layer is formed also during the summer period near the bottom. This layer spreads from the southern part of the sea, where end-brine is discharged to the sea from the Israeli and Jordanian salt plants' evaporation ponds. The end-brine has extremely high salinity ($\sim\,350 g/kg$) and, in spite of the high temperatures ($ \sim\,45^\circ\,C$), high density ($1350 kg/m^3$), it therefore spreads as a gravitational current in the Dead Sea deep basin.
Estimation of the density ratio ($R_{\rho}$) for the Dead Sea water (where measurements of water salinity is quite difficult) was done using quasi-salinity ($\sigma_{32}$) and potential temperature (\theta):
~ $R_{\rho}= [\alpha(\partial\theta/\partial z)]/[\beta(\partial \sigma_{32}/\partial z)]$, where $\alpha$ and $\beta$ are temperature expansion and quasi-salinity contraction coefficients respectively. The values of $\alpha$ and $\beta$ for the Dead Sea water were defined from water samples collected during 2008. The $R_{\rho}$ values confirm that the summer Dead Sea thermohaline structure is appropriate for double diffusion mixing. A salt fingers regime beneath the UML ($1.3< R_{\rho} |
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