The ice directly below the wire melts because the increased pressure lowers the melting point of the ice, hence the wire falls through the water formed. Above the water, decrease in pressure rises the freezing point of the melted ice and the water freezes again. On refreezing it liberates latent heat which is conducted by the wire to melt more ice beneath it. The process is repeated till the wire passes right through the ice block without cutting it into two. When we press two pieces of ice. blocks one against the other, they stick together. The increased pressure lowers the melting point of ice. The melted ice flows away to places of lower pressure. There, it refreezes, binding the two pieces of ice together.