From Ocean Skin to Submesoscales: A Journey Through Upper Ocean Physics
The upper few meters of the ocean are a complex and turbulent environment where winds, waves, and currents interact to shape weather, climate, and the marine ecosystem. Accurately forecasting this region is a grand challenge, requiring us to bridge the vast gap between small-scale physics and global ocean circulation. This seminar tells the story of a multi-year research journey that began with a specific question about turbulence and evolved to tackle the larger, more complex dynamics of ocean fronts.
Our story begins with an investigation into Langmuir turbulence, a wave-driven mixing process. However, extensive airborne and in-situ observations revealed a picture more complex than theory suggested; the ocean surface was not dominated by orderly Langmuir cells, but by a chaotic field of sharp, submesoscale features. This forced a pivot in our approach, leading to a series of field and laboratory experiments (at the SUSTAIN facility) to quantify how various forcing mechanisms combine to drive upper ocean mixing. This work directly led to the testing and significant improvement of turbulence closure schemes within operational Navy ocean models (NCOM).
Along the way, we uncovered unexpected physics. We found that under certain conditions, steep, young waves can paradoxically reduce ocean turbulence by creating an "airflow separation" effect that throttles momentum transfer from the wind to the water. This discovery illuminated a key weakness in existing models. Following the trail of the chaotic features we first observed, we then launched a massive observational campaign at the Gulf Stream's north wall. Using research vessels, aircraft, and drones, we compiled a first-of-its-kind library of frontal scenarios to test existing theories of frontal instability. This ongoing work is now setting the stage for our next project: quantifying how these powerful fronts alter the surface wave field, a critical and poorly forecasted hazard for maritime operations.
This seminar will connect these threads, showing how a focused study of small-scale physics can lead to unexpected discoveries and lay the groundwork for a broader understanding of the submesoscale processes that govern our oceans.
