Turbulence Profiling

Turbulence profilers reveal the hidden chaos of the ocean. They can identify the swirling vertical 'eddies' (circular currents of water or air that break off from a main flow, creating small, rotating vortices) that transport water between layers, the "fingers" of water probing from one mass into another, and the hotspots where mixing is most intense.

This small-scale mixing has a huge impact on our global climate because it controls how much heat and carbon get transported from the surface down into the deep ocean. When surface waters mix well with deeper layers, the heat and carbon dioxide the ocean has absorbed get spread throughout its depths. When that mixing weakens, the heat and carbon build up near the surface, which affects our atmosphere and the pace of climate change.

The turbulence technologies we use at NOC can investigate oceanic flows across an enormous range of scales, from eddies larger than cities down to the tiny, millimetre-scale swirls where water properties finally blend completely.

It’s the mixing processes happening across this huge range of scales that ultimately shape the ocean’s large-scale structure. They determine the rate at which crucial things like heat and carbon are transported around the planet. Our large-scale models can’t be accurate without understanding how all this small-scale turbulence adds up.

We have a whole toolbox of platforms for measuring turbulence, and we choose the right one for the specific scientific question we’re asking:

• Vessel-Deployed Profilers: Some profilers are connected to our ships by cables, which gives us real-time control. Others are "free-falling" systems that are released from the ship and recovered later, which offers more flexibility.
• Autonomous Platforms: Our gliders are long-duration explorers that can collect turbulence data for weeks or months at a time. Our Autonomous Underwater Vehicles (AUVs) are precision navigators that can get into tricky spots to investigate turbulence around specific features like the sides of an underwater mountain.

This diversity of platforms means we can measure turbulence in almost any ocean environment imaginable.

Ocean models rely on "parameterisations," which are simplified representations, or "best guesses," for processes that are too small for the model to simulate directly. Without real-world turbulence measurements, these best guesses might not match reality.

Our direct observations of turbulence allow us to test these assumptions, tune the models for specific environments, and reveal the real-world physics that drives the mixing.

It might seem strange that centimetre-scale turbulence can affect our entire planet’s climate, but the cumulative effect of all this small-scale mixing across the global ocean determines some fundamental properties. It affects how quickly the deep ocean warms, how much CO₂ the ocean can absorb, and where nutrients are supplied to support marine life. Getting the small-scale physics right is essential for making accurate large-scale predictions.

Advances in sensor technology and autonomous platforms are constantly expanding what’s possible. In the future, we’ll see longer-duration autonomous missions that can capture how turbulence changes with the seasons, and even higher-resolution measurements that will reveal ever-finer details.

As the ocean warms, its layers are changing, and this might be dramatically shifting the patterns of turbulent mixing. Understanding these changes requires long-term observation programmes that can track how turbulence is evolving over years and decades.

From the surface, the ocean might look smooth and calm, but underneath it’s a dynamic and chaotic world of turbulent eddies. Our turbulence profilers are the tools that reveal this hidden dynamism, measuring the centimetre-scale physics that ultimately determines the ocean’s role in regulating our climate.