Remove all loose snow that may have accumulated on the ice with your shovel, and locate the ice edge.
Press against the ice edge with your shovel slowly and in an upward motion. Do not chip at the ice with the shovel as this could gouge the deck surface. This is a long and arduous process.
Pour a bucket of hot water over the stubborn area If you are unable to clear all the ice in step two. This should melt the thicker sheets of ice enough to allow you to continue to clear with the shovel.
Spread rock salt or calcium chloride over the iced areas and wait for them to melt if time is not an issue. Most composite decking materials have no restriction against using these products; however, check with the manufacturer of your specific product to ensure this will not adversely effect or stain the surface.
Spread a layer of rock salt, calcium chloride or cat litter on the deck after all ice has been removed to prevent further build up. All three options are easily cleaned off with a hose after the cold snap has passed.