Abstract

The sinking speed, and hence export rate, of marine snow particles is highly dependent on their size, which is controlled by aggregation and disaggregation processes. Physical aggregation occurs primarily due to turbulence and differential settling. Most ocean models do not have sufficient resolution to capture three-dimensional turbulence, and typical parameterisations of turbulent shear neglect small-scale variability. Additionally, many process-based studies of marine snow aggregation are one-dimensional and hence do not capture horizontal variation in the turbulent shear rate. Here, we investigate marine snow aggregation in upper ocean turbulence by performing a series of high-resolution large eddy simulations (LES) coupled with a model for particle aggregation. The defining feature of LES is that they directly resolve the largest three-dimensional turbulent motions and hence capture spatial variability in the shear rate. We focus on the influence of advection and spatially varying turbulence across a range of lengthscales, including the submesoscale. Previous work has shown that submesoscale eddies (< 10 km) modify small-scale turbulence, and we assess the importance of this effect on the aggregation and export rates of marine snow.