I am reading that while Arctic sea ice is shrinking in area, Antarctic sea ice (shelf ice) is increasing in area. I think you're right, that the "mass loss process" for Antarctic shelf ice is iceberg calving (same for Greenland shelf ice, a huge such event sank the Titanic), some no doubt is also due to melting. Another question is whether expanding shelf ice in the Antarctic is owing to faster movement of continental glaciers. This could in turn be owing to any of several factors.

Regarding what precisely will happen with global warming, it seems we won't know until it happens, and then, we likely won't know precisely why. For instance, with the melting of montane glaciers nearly worldwide, is that because of lower precipitation or higher temperatures above 3000 meters, or is it about soot blackening the surface of that ice? Disclaimer: I am an amateur.