Dwarf Alberta spruce are popular in landscapes because of the symmetrical conical shape. The top dieback won’t regrow, leaving the plant disfigured. You’ll need to decide if it will fit in your landscape as it is.
Troubleshooting the dieback reason, and stopping it if you choose to keep the tree, will take detective work on your part.
This article from Purdue Extension, Likely Culprits of Dieback, is a good place to begin your research. It includes a link to a more complete Purdue publication about stress related conifer dieback.
To have our help, provide complete history of the tree and growing conditions. Photos from further away showing the surrounding area is helpful. Clip off the dead part, looking carefully at the trunk. Cut back the dead limbs—any obvious sunken patches? Color normal?
If you remove the tree, take time to examine how deeply it was planted (look for the natural root flare). It should be at the soil line, but trees are often planted too deep, causing problems often years later.
If you dig out the stump, be watching for circling roots. As with being planted too deep, roots can girdle and kill a tree after years of robust growth.
Share photos if you’d like my comments about what you find.