Double diffusion
The accumulation of huge amounts of methane and CO2 in Lake Kivu is only possible since the deep-water below 250 m depth is virtually decoupled from the surface. The gases in the deep-water reside for many hundred years. The build-up and maintenance of the extremely stable stratification is accompained by double-diffusive convection.
This phenomenon allows heat to be transported out of the deep water more efficiently than salts and dissolved gases, preserving the stabilizing salinity gradient and weakening the destabilizing temperature gradient. The double-diffusive layering regime in Lake Kivu causes an astonishing staircase of about 340 well-mixed layers (m-scale), separated by thin but very stable interfaces (dm-scale).
To understand how such a stable structuring (with probably only weak turbulence) could evolve is one of the main goals of this project.
Contact person
Alfred Wueest, Tobias Sommer, Martin Schmid
Funding
First Results
- Schmid M., Busbridge M., Wüest A. (2010) Double-diffusive convection in Lake Kivu. Limnology and Oceanography, 55(1), 2010, 225–238 (pdf, 2.51MB)