The ice block at initial temperature T-is = O degrees C is fixed at the center of a long, prismatic enclosure with isothermal vertical walls and insulated horizontal walls. The enclosure is completely filled with water at initial temperature T-il = O degrees C. Six numerical simulations were performed by varying vertical wall temperatures from T-W = 2 to 12 degrees C (range of Rayleigh number from 4.22 x 10(6) to 2.28 x 10(7)). In the case of T-W > 8 degrees C the ice melts faster from above and for T-W < 8 degrees C from below. In the case of Tw = 8 degrees C, two vortices are separated by nearly vertical 4 degrees C isotherm and the average Nusselt number remains constant during the convection dominated regime. (c) 2006 Elsevier Ltd. All rights reserved.