Numerical simulation of upwelling currents in pockmarks,and data from the Inner Oslofjord, Norway

摘要

The deflection of oceanic or tidal currents intopockmarks has been studied by both general three-dimensional computational fluid dynamics simulations andacoustic measurements in a number of pockmarks in theInner Oslofjord, Norway. The modeling demonstratesupstream convergence of flow lines, followed by upwellingover the pockmark. This upwelling is an effect of deflectedregional currents, not of expulsion of fluids or gas from theseafloor, and is sufficiently strong to prevent the settling offine particles. The field measurements, although noisy atlow vertical velocities, are consistent with the hypothesis ofupwelling. The reduction in sedimentation rate inferredover the pockmarks (relative to that of the flat surroundingseabed) can explain the maintenance, or even deepening ofpockmarks in the absence of fluid or gas seepage. Thecurrent pattern may also have consequences for the marinebiology of pockmarks.