PhD Position Unravelling the Physics Controlling the Atlantic Meridional Overturning Circulation

Dear colleagues

Within my research group I have an opening for a PhD student to work on the physics of the Atlantic Meridional Overturning Circulation, using realistic and idealized models [project abstract below for more details on the plan]

Applications are welcomed until mid-September.

In the Dutch system, PhDs become paid university employees for a 4-yr period but can also still enjoy the student facilities on campus. They spend their time almost entirely on their research project, except for tasks in assisting with education [max 10-15% of their time, typically grading exams, co-advising BSc and MSc students]. We expect they have a relevant education at MSc level when they start, although if needed they can take MSc courses / attend summer schools.

Feel free to forward the information to potential candidates.


Caroline Katsman


Prof. Dr. C.A. (Caroline) Katsman

Environmental Fluid Mechanics / Hydraulic Engineering

Civil Engineering and Geosciences

Delft University of Technology, NL

The Atlantic Meridional Overturning Circulation (AMOC), characterized by northward surface currents and dense return currents, transports vast amounts of heat to high latitudes, and is largely responsible for Western Europe’s relatively mild climate. Climate models project the AMOC will weaken substantially over the 21st century, which impacts weather, climate, sea level and the oceanic carbon cycle. Ground-breaking new observations have led to a major change in our view on the AMOC, as they revealed that the circulation in the eastern subpolar North Atlantic dominates over that in the west. Notably, climate models tend to simulate the opposite. This illustrates their limited skills in representing key AMOC features and the underlying lack of in-depth understanding of its physical controls. This obviously casts doubt on the reliability of scenarios of future AMOC changes that rely on such models.

From theory and idealized modelling studies it is known that three processes in concert determine the AMOC in density space: (1) densewater formation in the interior of marginal seas and its subsequent export, (2) dense water formation within the boundary current system, and (3) the exchange of waters of differing density with the (sub-)Arctic via overflows. However, their relative importance for shaping the AMOC and feedbacks between them are still unknown. Moreover, both are expected to vary strongly across the subpolar North Atlantic since the key factors regulating their physics (eddy dynamics, surface forcing) vary as well. The observations only register the net effect of these processes, and hence careful analysis of ocean models is imperative to address this knowledge gap.

Here, analyses of realistic and idealized model simulations are combined to exploit the capabilities of both. First, the contributions of the three processes controlling the AMOC are quantified in sub-regions of the subpolar North Atlantic Ocean from a state-of-the-art model simulation, in depth and density space. Next, their sensitivity to oceanic and atmospheric conditions is systematically explored using an idealized model, which facilitates the qualitative identification of cause-and- effect relations and interdependencies. It provides crucial guidance for the final step: the quantitative analysis and interpretation of AMOC variations from the state-of-the-art model simulation. In all, the the project is expected to provide a robust framework to evaluate the skills of models in simulating the AMOC, help establish strategies for improving them, and aid the interpretation of observed AMOC variations.

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