Effect of physical variables on particle critical erosion shear stress: Hydrostatic pressure, slope and changes in water density

Abstract

In recent years, the importance of organo-mineral aggregates (OMAs) in the transport of organic material from the continental shelf to the deep ocean floor has been recognized. Attempts to model the transport of these OMAs rely on measurements of several physical parameters, such as the critical erosion shear stress. However, due to technical constraints, such measurements are not done in situ, making it difficult to assess the impact of environmental parameters on the measurements made, and their accuracy in representing the study site. Changes in hydrostatic pressure, slope angle and water density potentially can affect the critical erosion shear stress of OMAs. Using new methodologies, we found no measurable effect of hydrostatic pressure variation on the OMAs' resuspension behavior. Changes in slope angle resulted in the decrease of u∗ cri up to 35%. The u∗ cri decreased by 9% with an exchange with denser water, and it increased by 6% with an exchange with lighter water. These changes were temporary, and after a 3-h stabilization the u∗ cri returned to the original value. We will discuss the future applications of these results on modeling of particle transport.