J. Hernlund $^{a}$, P.J. Tackley $^{a}$
$^{a}$ Department of Earth and Space Sciences, University of California, Los Angeles.
The presence of partial melt has been proposed to explain the occurrence of ultra-low velocity zones (ULVZs) at the base of the mantle (eg. Williams and Garnero, 1996). We present simulations of mantle convection in which partial melting occurs in the lower boundary layer and contributes to buoyancy. The dynamic feedback generated by the presence of partial melt can induce local small-scale convection within the warmest regions of D” which may play an important role in heat transfer across the core-mantle boundary and in the nucleation of plumes. We explore two end-member scenarios: one in which melt is less dense than the solid matrix (eg. Zerr and Boehler, 1998) which encourages upwelling flow and another in which melt is more dense (eg. Ohtani and Maeda, 2001) and tends to induce downwelling flow at the base of the mantle. If melt segregation is allowed to occur, the latter scenario may provide a dynamical mechanism that allows for the creation, maintenance, and continual re-supply of distinct local chemical reservoirs within D”.