Airborne blue lidar reveals the ocean’s hidden biological engine in the South China Sea

The ocean’s biological carbon pump, a critical climate regulator, is driven by phytoplankton ecosystems hidden from satellites. This observational blind spot has left the dynamics of the crucial subsurface chlorophyll maximum layer—a key engine of ocean productivity—unquantified across large scales. Here, we address this limitation with an airborne blue lidar system, engineered with a deep-penetrating blue laser (486 nm) and a hybrid detector to achieve extended profiling depth and dynamic range. During campaigns in the South China Sea, our validated system produced continuous, high-resolution profiles of chlorophyll architecture down to 100 meters, nearly doubling the reach of existing lidar technology. This capability provides a direct means to quantify the spatial heterogeneity of subsurface chlorophyll maximum layers, shifting the characterization of the ocean’s carbon cycle from an inferred picture to a directly observed reality. Our work provides a technological basis for next-generation of space-based missions to monitor the ocean’s interior.