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Lake Kivu - turbulence and double diffusion in permanent stratification

Titel Englisch Lake Kivu - turbulence and double diffusion in permanent stratification
Gesuchsteller/in Wüest Alfred
Nummer 122183
Förderungsinstrument Projektförderung (Abt. I-III)
Forschungseinrichtung Angewandte Gewässerökologie Forschungszentrum für Limnologie EAWAG Kastanienbaum
Hochschule Eidg. Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz - EAWAG
Hauptdisziplin Hydrologie, Limnologie, Glaziologie
Beginn/Ende 01.03.2009 - 29.02.2012
Bewilligter Betrag 332'256.00
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Keywords (17)

Double diffusion; lakes and reservoirs; methane; microsensors; microstructure; small-scale turbulence; meromixis; permanent stratification; turbulence modelling; Double diffusion; methane; microstructure; microsensors; small-scale turbulence; lakes and reservoirs; steps and layers; unstable boundary layer

Lay Summary (Englisch)

Lead
Lay summary

of carbondioxide and the water column is strongly and permanently density-stratified. Here,we want to explain the build-up of this unusual vertical stratification and itstemporal evolution. We also want to understand the build-up of the enormousmethane reservoir in Lake Kivu over centuries. Therefore, our results are alsoof economic interest: To avoid the risk of a gas eruption, the two riparian governmentshave decided to use the methane, worth > 20 billion US dollars. Therefore,it is of great interest to better quantify the methane production and verticalfluxes.3 of methane and ~300 km3The 485 m deepLake Kivu (Rwanda, DR Congo) is a fascinating and unique natural water body: Itcontains ~60 km

 

Due to sub-aquaticinputs of salty and carbon dioxide-rich water, Lake Kivu is strongly andpermanently stratified. This stratification is insofar unique, as the lakewater contains four components affecting water density. Whereas salt and carbondioxide increase the density in deeper layers, the temperature and methanereduce the density with greater depth. This close competition betweenincreasing and decreasing density leads to a so-called double-diffusivelayering, which causes an astonishing staircase of about 300 well-mixed layers(of ~1 m vertical thickness), separated by thin but very stable interfaces (of~1 dm vertical thickness).

 

So far we could demonstratethat it is possible to resolve - with specialized microstructure sensors - the verticalstructures of salinity down to 1mm and vertical structures of temperature downto 1 cm. With this high resolution we could show that the inner core of theinterfaces are laminar and the outer boundary of the interface form an unstableboundary layer of a few mm to cm thickness. This unstable boundary layer is theresult of the faster (and therefore broader) diffusion of temperature versusthe slower (and therefore narrowed spread) of salinity. Those unstable boundarylayers form the source of the convective mixing in the adjacent mixed layersabove and below any of those interfaces.

 

This project willmake a significant contribution to (1) re­search of double-diffusive regimes wherefour components (salt, carbon dioxide, methane, and temperature) contribute tothe vertical density structure, and (2) to the benefit of an optimized planningof the methane extraction.

 

For background information on Lake Kivu

http://www.eawag.ch/forschung/surf/gruppen/kivu/methane_harvesting/index_EN

 

For an introduction to double diffusion

http://www.eawag.ch/forschung/surf/gruppen/kivu/publications/2012_carpenter.pdf

Direktlink auf Lay Summary Letzte Aktualisierung: 21.02.2013

Verantw. Gesuchsteller/in und weitere Gesuchstellende

Mitarbeitende

Publikationen

Publikation
Minimal model for double diffusion and its application to Kivu, Nyos, and Powell Lake
(2015), Minimal model for double diffusion and its application to Kivu, Nyos, and Powell Lake, in Journal of Geophysical Research - Oceans, 120(9), 6202-6224.
Double diffusion in saline Powell Lake, British Columbia
(2014), Double diffusion in saline Powell Lake, British Columbia, in Journal of Physical Ocenaography, 44(11), 2893-2908.
Double-diffusive interfaces in Lake Kivu reproduced by direct numerical simulations.
(2014), Double-diffusive interfaces in Lake Kivu reproduced by direct numerical simulations., in Geophysical Research Letters, 41, 5114-5121.
Double diffusion in Lake Kivu
(2013), Double diffusion in Lake Kivu.
Interface structure and flux laws in a natural double-diffusive layering
(2013), Interface structure and flux laws in a natural double-diffusive layering, in Journal of Geophysical Research - Oceans, 118(11), 6092-6106.
Revisiting microstructure sensor responses with implications for double-diffusive fluxes
(2013), Revisiting microstructure sensor responses with implications for double-diffusive fluxes, in J. of Atmospheric and Oceanic Technology, 30(8), 1907-1923.
Diffusive-type of double diffusion in lakes - a review.
(2012), Diffusive-type of double diffusion in lakes - a review., 271-284.
Simulations of a double-diffusive interface in the diffusive convection regime
(2012), Simulations of a double-diffusive interface in the diffusive convection regime, in Journal Fluid Mechanics, 711, 411-436.
Temperature steps in salty seas
(2012), Temperature steps in salty seas, in Physics Today, 65(3), 66-67.
Double-diffusive convection in Lake Kivu.
(2010), Double-diffusive convection in Lake Kivu., in Limnology and Oceanography, 55(1), 225-238.
Stability of a double-diffusive interface in the diffusive convection regime.
, Stability of a double-diffusive interface in the diffusive convection regime., in Journal of Physical Ocenaography, 42(6).
Stratificaion, Mixing and Transport Processes in Lake Kivu.
, Stratificaion, Mixing and Transport Processes in Lake Kivu..

Zusammenarbeit

Gruppe / Person Land
Formen der Zusammenarbeit
Prof Marco Toffolon University of Trento, I Italien (Europa)
- vertiefter/weiterführender Austausch von Ansätzen, Methoden oder Resultaten
- Publikation
- Austausch von Mitarbeitern

Wissenschaftliche Veranstaltungen

Aktiver Beitrag

Titel Art des Beitrags Titel des Artikels oder Beitrages Datum Ort Beteiligte Personen
Workshop Aphys - SUPSI Vortrag im Rahmen einer Tagung Future ideas for Cadagno 19.10.2016 Lucerne, Schweiz Sommer Tobias;
18th Workshop on Physical Processes in Natural Waters Vortrag im Rahmen einer Tagung Bacteria cause mixing in Lago di Cadagno, Switzerland. 25.08.2016 Landau, Deutschland Wüest Alfred; Sommer Tobias;
CSF Conference Vortrag im Rahmen einer Tagung Fluid Mechanics an dCollective Behavior: From Cells to Organisms 03.04.2016 Ascona, Schweiz Wüest Alfred; Sommer Tobias;
Workshop on Double Diffusion Vortrag im Rahmen einer Tagung Insights from investigating double-diffusive convection in deep and strongly stratified lake 09.11.2015 Oaxaca, Mexiko Sommer Tobias; Wüest Alfred;
IBP congress, ETH Zürich Vortrag im Rahmen einer Tagung Climbing the Lake Kivu staircase 13.04.2012 Zürich, Schweiz Wüest Alfred; Sommer Tobias; Carpenter Jeffrey Richard;
International Symposium on Stratified Flows Vortrag im Rahmen einer Tagung Double-diffusive staircases modeling 22.08.2011 Rom, Italien Carpenter Jeffrey Richard; Wüest Alfred; Sommer Tobias;
EPFDC Conference 2011 Vortrag im Rahmen einer Tagung Temperature and salinity microstructure of a double-diffusive 09.08.2011 Göttingen, Deutschland Carpenter Jeffrey Richard; Wüest Alfred; Sommer Tobias;
Euromech Colloquium 519: Mixing and dispersion in flows dominated by rotation and buoyancy Vortrag im Rahmen einer Tagung Direct numerical simulation of diffusive convection with 20.06.2010 Limburg, Niederlande Wüest Alfred; Sommer Tobias; Carpenter Jeffrey Richard;


Veranstaltungen zum Wissenstransfer

Aktiver Beitrag

Titel Art des Beitrags Titel des Artikels oder Beitrages Datum Ort Beteiligte Personen
Lake Kivu Workshop Vortrag 08.02.2011 Gisenyi, Ruanda


Auszeichnungen

Titel Jahr
ETH Zürich medallion for exceptional thesis 2013

Verbundene Projekte

Nummer Titel Start Förderungsinstrument
123923 Lake Kivu: Learning from the past for managing its future 01.06.2009 Resource not found: '20438a61-de74-41e3-9fb1-8132973c4a1f'
140538 Lake Kivu - turbulence and double diffusion in permanent stratification 01.04.2012 Projektförderung (Abt. I-III)

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