Nuclear energy and sea level rise

Feb 2011
The world's nuclear electrical capacity in the year 2000 was 350 GWe. If all the waste heat from operating these nuclear plants for one year were used to melt ice (initially @ 0 deg celsius) from the Antarctic ice cap, what would be the increase in the depth of oceans? Assume that 70% of the surface area of Earth is covered with water, and that the nuclear power reactors operate at an efficiency of 30 percent. The radius of Earth is 6400 km.

MY WORK: For this question, I used efficiency and the electrical capacity to figure out the total P_in. After that I found out heat energy by subtracting total P_out from the capacity. Afterward, I used Q = m*L to figure out the mass of water melted and then divided that number by the density of water. I got 23.202 km^3 of added melted water. However, I'm stuck here and don't know how to figure out the increase in depth with the value of increased volume? Any insight/guidance would be greatly appreciated. Thanks.