Yuchen Ma马玉晨

Postdoctoral Associate · Department of Applied Mathematics and Theoretical Physics, University of Cambridge

I am a physicist who works on the ocean. I study turbulence and waves in the ocean interior and at its boundaries, with theory, numerical simulations and observations.

What I work on Publications Get in touch
Surface currents of the North Atlantic rendered as flowing white streaks on a dark blue ocean, with the Gulf Stream and its eddies
Surface currents in the North Atlantic from NASA's Perpetual Ocean, built from the ECCO2 ocean model. Image: NASA/Goddard Space Flight Center Scientific Visualization Studio.
Yuchen Ma

About

My training was in physics, and I still think like a physicist. When I look at the ocean I want to understand why it does what it does, and I keep going until I can write the reason down, at least roughly.

The ocean is a good place for this kind of question. It has motions on all scales, from the basin-scale circulation down to turbulence of a few centimetres, and the small scales matter: they control how heat and salt are mixed, and through that what the large-scale circulation can do. What the ocean does for the climate, moving heat and carbon around the planet and melting ice at the edges, depends on processes in its interior and at its boundaries, where we have the fewest measurements and where climate models have to rely on parameterisations.

My questions usually come from observations. There is something interesting in the data, I try to find the mechanism behind it, and I write down a model that is simple enough to understand. I test the model with idealised simulations and go back to the observations to see whether they agree; when the question needs it I also do realistic modelling. A theory is only useful if it can be compared with what is actually measured, so I value observations a great deal, even though my own work is theory and modelling. This mix of applied mathematics, physics and earth science is geophysical fluid dynamics, and I am always happy to talk with people who work on fluids with similar tools.

Research

What I work on

Why is the Arctic interior arranged in steps, and how much heat do they let through?

Below the Arctic sea ice there is enough heat to melt all of it. A strong salinity stratification, with staircases in it, keeps the heat down.

Warm Atlantic water sits a few hundred metres below the ice. It is held there by a strong salinity stratification, and within that stratification the temperature and salinity profiles are arranged in staircases: well-mixed layers separated by sharp interfaces. Each interface limits the upward heat flux, and the turbulence inside the layers is double-diffusive. Whether these staircases survive as the Arctic warms and freshens is part of what determines how fast the ice feels the heat below it.

In my PhD I proposed a mechanism for how the staircases form, an instability that appears when double diffusion and stratified turbulence act together, and tested it with direct numerical simulations. I then looked at how much heat passes through a staircase when turbulence is added. What I would like to know now is what happens to them as the Arctic changes.

Potential temperature and salinity against depth in the Arctic Ocean, with insets zooming on the staircase between 240 and 290 metres
Temperature and salinity in the Arctic Ocean: cold water above, the warm Atlantic layer below, and in the insets the staircase in between 240–290 m, from Timmermans et al (2008).
Staircase formation in a direct numerical simulation.

Publications

Papers

Two papers were highlighted as Editors' Suggestions in Physical Review Fluids. The staircase work was covered by U of T News and The Guardian.

Experience

Where I have been

  • 2025 –Postdoctoral Associate, University of Cambridge
    DAMTP, with John R. Taylor. Turbulence and melt at Greenland ice–ocean interfaces.
  • 2023 – 2025Postdoctoral Associate, Massachusetts Institute of Technology
    EAPS, with Raffaele Ferrari. Turbulence and internal waves at the ocean bottom.
  • 2023Postdoctoral Associate, University of Toronto
    Physics, with W. Richard Peltier. Turbulence in thermohaline staircases.
  • 2016 – 2022Ph.D. in Physics, University of Toronto
    Supervised by W. Richard Peltier. Double-diffusive turbulence and the formation of thermohaline staircases.
  • 2012 – 2016B.Sc. in Theoretical Physics, University of Science and Technology of China
    Yan Jici Talent Students Program in Physics.

Contact

Come and talk

I am generally interested in physical oceanography, fluid mechanics and climate science, and happy to talk about any of them. Write to me.

Emailym460@cam.ac.uk
OfficeCentre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, UK