Since December 2023, Dennis Vermeulen has been engaged as a PhD candidate under the supervision of Prof. Dr. Caroline Katsman and Dr. Renske Gelderloos, working on the project North Atlantic CLUEDO: Controls on Light Upper ocean waters Entering the Deep Ocean. He is affiliated with the Environmental Fluid Mechanics section within the department of Hydraulic Engineering, part of the faculty of Civil Engineering and Geosciences at Delft University of Technology.

In this project concerning ocean circulation in the subpolar region of the North Atlantic, Dennis investigates the Atlantic Meridional Overturning Circulation (AMOC). The AMOC carries vast amounts of heat from the equator to high latitudes, largely accounting for Western Europe's comparatively mild climate. In response to global warming, the AMOC is anticipated to significantly weaken, affecting regional climate and sea levels. However, the representation of the AMOC in climate models exhibits deficiencies, which casts doubts on the reliability of future changes projected by these same models. As phrased in the IPCC 6th Assessment Report: ”this results in low confidence in quantitative projections of AMOC decline in the 21st century, despite the high confidence in the future decline as a qualitative feature based on process understanding”.

Dennis therefore aims to disentangle and quantify the physical processes underpinning the overturning in the North Atlantic Ocean. For this, he will use both state-of-the-art climate models and a conceptual model he will develop himself, which both allow the study of the full three-dimensional structure of the AMOC system, rather than studying a condensed 2D (or 1D) perspective. Doing so, he will quantify the contributions of physical processes shaping the AMOC in depth and density space in various sub-basins of the subpolar Atlantic Ocean, and will systematically explore the sensitivity of each of these processes to oceanic and atmospheric conditions, gaining more insight in potential feedbacks between them. With this, Dennis aims to provide guidance for the interpretation of ocean observations and on assessing and improving the skills of ocean and climate models in representing AMOC physics, thus improving the reliability of projected AMOC changes and its impacts.

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