If you think melting sea ice will raise the ocean's level try this.
Fill a glass full of ice, all it will hold but not over the top. Then fill the glass full of water and set it on the kitchen counter. See if the glass runs over as the ice melts. I won't. Actually the level of the water will drop as the ice melts because the ice contains air. This is also true with sea ice. Ocean levels have risen and fallen slightly over the eons because of melting land ice running into the seas but only slightly. The earth is already 70% water and the increase from melting ice is zilch.