Indeed, glaciers are literally ice-rivers [1], they flow from mountains down. Melting downstream near the sea/ocean will accelerate their disappearance and yield to global oceal level increase. Ronne Ice Shelf is like an ice-gulf, melting and separation of icebergs reclaims the ice allowing water getting deeper and deeper into Antarctica.
[1] https://youtu.be/he5QzhE7_g4?t=16