PhD topic proposal Long- and short term drivers of CO2 in Lake Geneva

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PhD topic proposal

Long- and short term drivers of CO2 in Lake Geneva

Location. Université de Lausanne, Faculté des Géosciences et Sciences de l’Environnement, Switzerland

Specialty. Physical and biogeochemical limnology

Institute. IDYST, Institut de Dynamique des Surfaces Terrestres/ Institute of Earth Surface Dynamics

Supervision. Prof ME Perga (UNIL), Dr D Bouffard (EAWAG)

Funding. SNF funding (CARBOGEN project) for 4 years. The contract implies a 20% teaching duty.

Starting Date: April 1st 2018

Deadline for application. December 21st 2017

Keywords. lake, CO2, metabolism, hydrodynamics, metabolism, biogeochemistry

Profile and skills required

Master in Biogeosciences, environmental physics or environmental sciences Skills in data analysis and modelling

Research context of the CARBOGEN project

If inland waters have recently been acknowledged as significant reactors of the global carbon cycle, light has been essentially shed on wetlands, permafrost and humic lakes, under the overwhelming paradigm that lake supersaturation with CO2 arises from metabolic processes. Within this picture, large and clearwater lakes have been largely overlooked, considered as neutral to the atmosphere. As a result, our knowledge about the carbon cycle in such lakes is clearly deficient. For instance, in Switzerland, a heuristic carbon budget attempted on the heavily studied and highly monitored Lake Geneva ended up unbalanced, C outputs being twice higher than the inputs. Estimated CO2 outgassing reaches surprisingly high numbers. Rough estimates suggest that the 10 largest Swiss lakes emit as much CO2 as fossil fuel combustion of total Swiss agriculture. The example of Switzerland shows that large and clearwater lakes could be a central feature of a national carbon budget and plead for a revision of our C conception in such environments.
Project CARBOGEN assumes that (1) key processes in lake carbon cycling are inaccurately scaled or remain missing, (2) C is controlled by intricated physical and biogeochemical processes which relative contributions depend on the time and space scales of observation, (3) lakes carbon cycling is highly sensitive to human and climate disturbances. The motive of CARBOGEN is therefore to address the carbon cycle of Lake Geneva through two objectives. The first one is to close the lake carbon budget by refining flux estimates accounting for the large temporal and spatial variability of the carbon processes and by identifying and quantifying missing sources. The second aims at untying the mechanisms behind the long-term C variability, and therefore to quantify the human contribution to such changes. For that purpose, CARBOGEN relies on an integrated, process oriented perspective on the carbon cycle of Lake Geneva, combining field surveys, high-frequency monitoring, bioassays and modelling

Project description

Within CARBOGEN, the research topic of the PhD candidate will focus on the short- and long term drivers of Lake Geneva CO2 concentrations, with a more specific attention on the role played by vertical and lateral transport. CO2 concentrations in lakes have long been thought to be essentially controlled by lake metabolism but this long-standing paradigm is being considerably challenged, while the role of chemical and hydrological processes are just being reconsidered. Previous works on Lake Geneva have shown that the drivers of CO2 variability in Lake Geneva, such as the underlying mechanisms, appear to differ depending on the time and space scales of observations. They highlight the necessity for a process-oriented approach to understand C-cycling in Lake Geneva, that fully integrates biogeochemistry and hydrodynamics.

The PhD candidate is expected to untie the drivers of the vertical and temporal (at short and longer time scale) of Lake Geneva CO2, using pluri-decennial monitoring dataseries and high-frequency measurements form an automated platform. Data use and interpretation will be based from both deductive (data mining) and inductive approaches (simple 1D modelling combining physics to biogeochemical processes).

The PhD candidate is expected to work in strong collaboration with a second PhD candidate from the CARBOGEN project focusing on spatial variability in C processes in Lake Geneva. This project implies a true co-supervision shared between Prof Perga and Dr Bouffard, thereby requiring regular trips between their institutions.

Contact details and application

For any questions, contact
Applications are to be sent directly by e-mail and should include a CV and motivation letter along with the name of three references.


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