Towards a Lagrangian-informed representation of ocean particulate export: from small-scale turbulence to climate models

The ocean biological carbon pump transfers particulate organic matter (POM) from surface waters to the deep ocean, playing a key role in long-term sequestration of organic matter. Small-scale turbulence and stratification strongly influence particle sinking, yet these processes are poorly represented in global models, which rely on simplified parameterizations.

We investigate these effects using high-resolution direct numerical simulations (DNS) of stratified turbulence, designed to capture small-scale ocean dynamics, coupled with a Lagrangian inertial particle model. By resolving turbulent structures and particle–fluid interactions, we aim to quantify how turbulence intensity, stratification, and particle properties control sinking velocities and export efficiency. Multiple particle types are tracked under ocean-relevant conditions, constrained using oceanographic observations and reanalysis data to provide realistic ranges for turbulence, stratification, and vertical shear.

To bridge microscale processes to large-scale modeling, we incorporate DNS-derived insights into climate simulations using the Earth System Model EC-Earth, a fully coupled atmosphere–ocean configuration. The ocean and its biogeochemistry are simulated with NEMO-PISCES, and the atmosphere with OIFS. This approach allows us to assess how unresolved turbulence and particle dynamics affect particulate export at global scales. By combining turbulence-resolved Lagrangian simulations with global climate experiments, this work aims to reduce uncertainties in particle transport and improve understanding of biogeochemical microscale processes and their climate feedbacks. Simulation data and tools will be openly available to enable further research on microscale ocean transport processes and their representation in global climate and ocean models.