Abyssal Pathways and the Northeast Pacific Double Silica Maximum

The silica field in the Northeast Pacific Basin has proved challenging to model with one-dimensional advection and diffusion. This study uses a recent potential vorticity- and salinity-conserving inverse estimate of steady-state circulation in the Upper Circumpolar and North Pacific Deep Water to model silica and radiocarbon fields in three-dimensions using a stochastic Lagrangian approach. The region’s diapycnal mixing is weak, and the bottom and mid-depth silica maxima are not simply connected by vertical processes within the basin. Instead, the double maxima can be explained by the juxtaposition of water mass pathways flowing largely along neutral density surfaces, combined with a latitude-dependent bottom source and modest water column regeneration.