Coral and float-derived observations of flow around SG_áan K_ínghlas-Bowie Seamount in the Northeast Pacific: revisiting the Taylor cone

Abstract

Seamounts are oases of life within the deep sea. Recruitment mechanisms to these isolated systems, where benthic larvae spend weeks or months in the pelagic, remain a mystery. Persistent closed circulation patterns ('Taylor cones') are proposed to increase local retention around these underwater mountains, but the idea remains controversial. Some coral species may help us understand this puzzle. Cold-water corals, such as Primnoa pacifica and Parastenella spp., grow slowly, orienting their fan perpendicular to, and curved towards, the mean-flow direction. We took advantage of these long-term natural current meters, using a combination of benthic imagery, sea-surface height, Argo trajectory, hydrographic, and reanalysis model data to examine flow around S$\underset{\_}{G}$áan $\underset{\_}{K}$ínghlas-Bowie Seamount (S$\underset{\_}{K}$-B) in the Northeast Pacific. We found that corals living on the seafloor on all sides of the seamount experienced a north to south flow (opposite to regional circulation), showing no evidence of a persistent closed circulation. We suggest that a combination of remotely generated internal tides breaking on the plateau and steering/rectification of local tides below 500m could cause these strong coherent bottom currents. Finally, we also observed transient clockwise circulation around the seamount when Haida Eddies became trapped. Eddies provide a regular mechanism for larval and food transport from the coast to S$\underset{\_}{K}$-B. Once trapped, the closed clockwise circulation lasts months and likely aids in local retention and self-recruitment. Our findings reveal the dynamic nature of flow over seamount-like features and the importance of understanding this complexity in the broader context of marine conservation.