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M5: Reducing Spurious Dissipation and Energetic Inconsistencies in Realistic Ocean Modelling Applications

Principal investigators: Prof. Hans Burchard (Leibniz Institute for Baltic Sea Research Warnemünde), Prof. Sergey Danilov (Alfred Wegener Institute for Polar and Marine Research), Prof. Armin Iske (University of Hamburg), Prof. Winnifried Wollner (University of Hamburg)

The project investigates important aspects of the Arbitrary Lagrangian-Eulerian (ALE) layer motion framework and high-order weighted essentially non-oscillatory (WENO) advection schemes, in order to fully exploit the potential of these new concepts in realistic ocean climate modelling applications. During the first phase, these concepts have been identified as the most promising techniques to significantly reduce spurious mixing in ocean models. However, now the efforts in basic research have to be extended to address emerged challenges related to general robustness and efficiency as well as other further mandatory model adjustments. The main goals are:

  • Development of a robust generalized layer motion algorithm based on Lagrangian layer motion and a combination of different regridding strategies.
  • Adaptation and optimization of high-order numerical schemes for remapping, internal pressure gradient and WENO advection to the resulting unstructured mesh layout with sloping layers in FESOM.
  • Development of new diagnostics for diapycnal mixing and internal pressure gradient errors to assess the energetic consistency of the newly designed model components.

With these efforts, we aim for enabling a new era of energy-consistent climate simulations, which will not be dominated by spurious numerical mixing anymore, but by the advanced and wellcalibrated physically-motivated mixing parameterizations developed in other subprojects of this CRC.

Summer School at Churchill College, Cambrige by Marika Federer and Boris Shaphkin (September 25)

We attended the two-week FDSE Summer School on Fluid Dynamics of Sustainability and the Environment at the University of Cambridge, held from September 1 to September 12, 2025. The event took place at Churchill College and was organized by the Department of Applied Mathematics and Theoretical Physics in collaboration with École Polytechnique in Paris. The summer school brought together international PhD students and early-career scientists from diverse backgrounds in earth sciences, engineering, and mathematics.

The program provided an excellent opportunity to deepen our understanding of the fluid-dynamical aspects of energy transition and climate change. Each day featured lectures on a variety of topics, including ocean dynamics, atmospheric flows, and ice sheet behavior, illustrating how fluid flow processes influence these complex systems. In addition, we participated in computational and laboratory exercises, which allowed us to gain practical experience with fluid instabilities and connect theoretical concepts to real-world applications.

The event also emphasized networking among participants and faculty, fostering an inspiring exchange of ideas with researchers from around the world. Outside of the academic program, we enjoyed exploring Cambridge and taking part in activities such as punting on the River Cam.

Overall, the summer school provided a valuable combination of scientific learning, hands-on experience, and international collaboration, an enriching experience for our research careers.

Research Stay in Boston by Tridib Banerjee (Oct 23)

Hi, my name is Tridib and this is a short report on my 2 months research stay at Massachusetts Institute of Technology, Boston, United States.

There is no way to begin this report without first thanking everyone involved in making it happen. I would like to express how grateful I am to everyone from TRR who helped me through the entire research stay. From planning to securing of funds. To the organizers and the Vorstand, thank you so much. I would also like to thank the responsible people from Constructor university for expediting the fund disbursement so that I could pursue the research at my desired dates. I would also like to thank my supervisor of the research stay Prof. Raffaele Ferrari, for being a terrific mentor (alongside postdoc Simone Silvestri) and sponsoring the discretionary funding to Massachusetts Institute of Technology. I would further like to thank Massachusetts Institute of Technology for making my immigration to US very easy. I would like to thank also my supervisor at TRR – Prof Sergey Danilov for always being available for consultations and helpful discussions and finally, also my current collaborators who kindly shared my workload so that I could focus on the research stay. Thank you all.

I joined the Climate Modelling Alliance to work in collaboration with California Institute of Technology and NASA, Jet Propulsion Laboratory. My role was to join the ocean modelling team at Massachusetts Institute of Technology and help them diagnose their new advection scheme using a diagnostic technique Me, Sergey Danilov, and Knut Klingbeil developed during my PhD. It was a great experience and I learned a lot during the process. Unlike the ocean model that I had worked with in Alfred Wegener Institute, the one I had to use during my research stay ran on GPUs instead of CPUs. This shift of compute architecture meant rethinking of even the fundamental mathematical operations. The work was initially planned to be concise but later, we realized it to be bigger and more important than expected. We ran several interesting experiments and, in the end, we began writing a new manuscript together. Currently, we are running more experiments and working towards finishing our manuscript. In summary, the stay in Boston impacted my career way more than I thought.

While I had my fair share of work to do in Boston, I also enjoyed my time there a lot. I fell in love with their research culture and found a family in my land-lady who was so generous and kind to me during my whole stay. I also went to Michigan to visit my actual family, watch my very first American Football, that too a classic Ohio versus Michigan which Michigan surprisingly won (it was a total pandemonium), and also have my very first American thanksgiving. I was extremely scared going to US but I had nothing but only fun during my entire stay. I would definitely do it again.