The influence of mesoscale and submesoscale circulations on carbon drawdown into the ocean In the northern Gulf of Mexico*

We explore the influence of mesoscale circulations on carbon drawdown in the Gulf of Mexico using numerical simulations performed with a model at 1-km horizontal resolution. Results are compared to field samples collected in 2012 from two sediment traps located at 27°22.5 N, 90°30.7 W (GC600) and 27°31.5 N, 89°42.6 W (AT357),  81 km apart. Through inverse calculations, model results indicate that cross-shore transport of riverine input induced by mesoscale eddies, and convergence and divergence processes at the scale of a few kilometers, significantly impact the trajectory of sinking particles and carbon drawdown. Also, the majority of modeled particles reach the bottom faster than would be expected by their sinking speeds alone. This finding is associated with submesoscale-induced horizontal convergence in the mixed layer that aggregates particles preferentially in downwelling regions, accelerating their descent. Furthermore, this study confirms that the cone of influence of vertical fluxes is highly variable in both space and time in the presence of an energetic eddy field.