Resolution-dependent variations of sinking Lagrangian particles in general circulation models

Any type of non-buoyant material in the ocean is transported horizontally by currents during its sinking journey. This lateral transport can be far from negligible for small sinking velocities. To estimate its magnitude and direction, the material is often modelled as a set of Lagrangian particles advected by current velocities that are obtained from Ocean General Circulation Models (OGCMs). State-of-the-art OGCMs are strongly eddying, providing results with a spatial resolution in the order of 10 km on a daily frequency. Many long term climate modelling simulations (e.g. in paleoclimate) rely on lower spatial resolution models that do not capture mesoscale features. It remains unclear how much the absence of mesoscale features in low-resolution models influences the Lagrangian particle transport. In this study, we simulate the transport of sinking Lagrangian particles using low- and high-resolution OGCMs, and assess the lateral transport differences resulting from the difference in spatial and temporal model resolution. We find major differences between the transport in the non-eddying OGCM and in the eddying OGCM. Addition of stochastic noise to the particle trajectories in the non-eddying OGCM parameterises the effect of eddies well in some cases (e.g. in the North Pacific gyre). The effect of a coarser temporal resolution (5-daily versus monthly) is smaller compared to a coarser spatial resolution (0.1$^{\circ}$ versus 1$^{\circ}$ horizontally). We recommend to apply sinking Lagrangian particles only with velocity fields from eddying OGCMs, requiring high-resolution models in e.g. paleoceanographic studies. To increase the accessibility of our particle trace simulations, we launch this http URL, an online tool to reconstruct the surface origin of sedimentary particles in a specific location.