Potential supervisors and the selection of potential PhD topics

You will find the description of a number of PhD topics further below. For you application, please choose between 1 - 3 PhD topics which are of particular interest to you. There is no need to get in touch with individual supervisors at this stage.

Specific projects, including a mutually beneficial advising arrangement within one of the department’s working groups, will be developed after the interviews with the prospective candidate only. To guide this process, candidates are asked to indicate a general area of interest, whether that be topical or methodological, and explain this interest in the context of their Letter of Motivation and the structure of the department.

MPI-MSchmidt, H. Ilyina, T. 
Stevens, B.N.A.Kapsch, M.N.A.
  Mikolajewicz, U. 
Uni HHN.A.N.A.N.A.N.A.

Additional selection of potential PhD topics

Ocean general circulation and biogeochemical components of Earth System Models currently suffer from a number of long-standing issues related to uncertainties in representing effects of mesoscale eddies and their variability due to a too coarse spatial resolution. The poor, or often absent, representation of mesoscale (2 km to 200 km) circulations in present climate models limits the ability to explore important Earth system questions with any fidelity.

This is especially true for the regions of the ocean, such as the Southern Ocean, which act as a major sink of carbon and heat, and where mesoscale processes play a fundamental role. By resolving mesoscale eddies that are decisive for these ocean processes, it is critical to study their impacts in new ways, even with relatively short (decadal to multi-decadal) simulations.

Using the new ocean model ICON with embedded ocean carbon cycle model HAMOCC, this project will address the questions:

  • How do eddies affect spatiotemporal variability of heat, carbon, and oxygen?
  • What is the impact of eddy-induced transports on the budgets of heat, carbon, and oxygen?

The project is part of the Hamburg’s Cluster of Excellence CLICCS within its subproject A6 (https://www.cliccs.uni-hamburg.de/research/theme-a/a6.html).

Due to increasing temperatures in the last decades, the Greenland ice sheet has lost a significant amount of mass. Recent studies have shown that with an ongoing warming, the Greenland ice sheet is likely to continue to lose mass and might reach a tipping point beyond which the ice sheet will not be able to regrow, even if atmospheric greenhouse gas concentrations would be lowered to preindustrial values again. While this has been studied with simple models before, a new developed comprehensive atmosphere-ocean-ice sheet-vegetation-solid earth model will be used here, allowing for a more realistic description of feedbacks between the Greenland ice sheet and other compartments of the climate system, including the atmosphere, ocean and solid earth. 

In this PhD project the stability of the Greenland ice sheet will be studied in the coupled climate-ice sheet-solid earth model MPI-ESM-mPISM-VILMA, developed by the ocean-physics group as part of the project PalMod. The student will perform model simulations under changing climate conditions and investigate if and when the Greenland ice sheet crosses a tipping point. The goal is to explore whether the Greenland ice sheet could potentially return to its present state if temperature trends would reverse or whether the ice sheet reaches a new stable state that differs from the present, hence, exhibits multiple steady states including hysteresis behavior. The work will contribute to a better understanding of the physical processes and feedbacks between the Greenland ice sheet and other compartments of the climate system.

One of the big emerging questions in climate science is how circulations change with warming, and to a lesser degree, how these changes influence the warming. One example of such a question relates to the distribution of stratocumulus clouds, which form under the subtropical summertime high-pressure regions that form over oceanic eastern boundary currents. Stratocumulus clouds have an important effect on how much solar energy the Earth absorbs, but their formation is influenced by the large-scale state of the atmosphere. For instance the stability and dryness of the lower troposphere, which depends on monsoon circulations that develop over the adjoining continents. Hence the question arises as to whether we understand what controls changes in lower tropospheric stability with warming, and infer what this means for the changes in cloudiness. Another example is how energy transport between the tropics and extratropics influences extra tropical humidity. Humidity is the leading contributor to Earth’s greenhouse effect and hence important for controlling surface temperature. As the tropics trap disproportionately more energy with warming they require increased export to the extra tropics. We aim to understand how this change influences the humidity of the extra tropics and hence Earth’s climate sensitivity.

Applicants with an interest in large-scale dynamical meteorology are especially encouraged to apply. Depending on the successful applicant's interests a suitable supervisory relationship will be established, perhaps also in cooperation with university group (Žagar or Mellado) at the Universität Hamburg.