Scientists using an innovative laser-equipped research platform have discovered a previously hidden environment that exists in the transitional zone between the air and the ocean surface.
The new research reveals two competing energy exchanges occurring between surface winds and the ocean, providing a deeper understanding of the intricate air-sea interaction that influences waves and other ocean surface phenomena.
Mapping the airflow above the ocean’s surface down to measurements of just millimeters, the research reveals that long and short waves interact with the wind in very different ways, which offers potentially new insights into the influence of these surface dynamics on climate and weather models, as well as how heat and gases move between the atmosphere and the ocean.
Laser Mapping Exposes Hidden Air–Sea Interactions
The research, led by Dr. Marc Buckley of the Hereon Institute of Coastal Ocean Dynamics, deployed a custom laser measurement system on board the Floating Instrument Platform (FLIP) in the Pacific Ocean.
Capturing detailed imagery of the airflow occurring just above the surface of the Pacific waters, the findings revealed two distinct wind-wave coupling processes—each one operating simultaneously but producing very different characteristics.
Short waves, which are approximately a meter long, move more slowly than the wind that meets the ocean surface, resulting in pressure differences as the wind separates over their crests and transfers its energy into the waves.
By contrast, long waves, which can stretch up to 100 meters in length, move significantly faster than the wind and produce their own distinctive airflow patterns. The combination of these distinctive processes occurring simultaneously across different regions of the wave field gives rise to a range of complex dynamics in the “hidden world” between the ocean and the near-surface winds.
Airflow Insights Could Transform Climate Models
The findings are significant, as the complex interplay between energy, heat, and greenhouse gas exchanges between the ocean and the atmosphere is a crucial driver of the planet’s climate and weather systems.
Although researchers have understood the underlying processes behind these phenomena for decades, a closer examination of the dynamics that cause them is beneficial, as the finer-scale mechanisms at work have proven difficult to measure in the past.
Building on their current work, Buckley and the team now aim to capture subsurface water movement with equal precision, which could help researchers assemble a more comprehensive picture of the dynamics occurring between the air and the sea.
“Until now, no one has measured the airflow this close to the ocean surface, let alone mapped the mechanisms of energy exchange at such a fine scale,” Buckley said in a statement.
“Our observations shed light on a physical frontier,” he says. “This will enable us to advance the theoretical framework and develop more accurate descriptions of air–sea exchange processes, which have so far been only partially understood.”
Lasers Capture the Ocean Surface in 3D
Fitted with a green laser capable of penetrating both air and water, the beam is scattered when laser light strikes water droplets carried in the air, which makes even the smallest amount of airflow movement visible.
By comparison, below the ocean surface, wind-driven ripples cause refraction of the laser’s light, which allowed the research team to produce maps of the water’s subtle contours.
The technology is based on what researchers call Particle Image Velocimetry (PIV), a technique known to fluid dynamics researchers that offers precision measurements of flow structure and wind speed.
Notably, this marks the first time PIV has been applied over the open ocean, allowing Buckley and the research team to produce simultaneous visualizations of both sides of the boundary between air and sea.
The team’s research was detailed in a recent paper, “Direct observations of airflow separation over ocean surface waves,” which was accepted for publication in Nature Communications.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.