Abstract
In the oceans of the low latitude, the surface water mass of high temperature and low density is contacted occasionally with the deeper water mass of low temperature and high density. For the particles of sedimentary origin settling in the water column of this situation, the settling velocity would be decreased sharply at the contact due to the sharp increases of density and viscosity. If the sedimentary particles are supplied into the water column continuously, they may be crowded at this horizon due to the sharp decrease of settling velocity, or they can be advected with some kinds of vortices which may occur at the contact. The mechanism was analyzed and the water masses of this situation was investigated in the oceans surrounding the Ryukyu Islands. The contacts of such water masses are well developed in the water columns at the passage region of the Kuroshio and the settling behaviors of sedimentary particles should be studied at this region in the future.
