Seamounts in a restless ocean: Response of passive tracers to sub‐tidal flow variability

Abstract

The action of sub‐tidal oceanic flow impinging on an isolated seamount, and its consequences for biological tracer patterns, was assessed using a three‐dimensional ocean circulation model. Passive tracers released above an isolated Gaussian seamount were exposed to variations of flow magnitude, frequency, direction and seamount height. The evolving patterns indicate significant qualitative differences: Steady and amplitude modulated unidirectional inflows generate advective downstream particle loss and patchiness. Non‐uniform inflow reduces advective particle loss, and tracers are systematically redistributed and aggregated around the seamount summit. Tracer retention is mainly controlled by flow magnitude and summit depth. Variations of flow period were of lesser importance. Two important biological implications arise from this study: First, particle dynamics at isolated seamounts is strongly constrained by mesoscale variability of the sub‐tidal far field flow. Secondly, the influence of seamounts on particle distribution is not restricted to local and small‐scale phenomena, but can penetrate deep into the oceanic far field on a scale of tens to hundreds of kilometers.