The ice thickens from the edge to the middle of the ice sheet. The thicker the ice, the faster the ice streams pull ice from the ice sheet. This means that once the ice streams start to pull ice from the ice sheet, the ice gets thicker and thicker and the ice streams pull faster and faster. The ice has to have somewhere to go. In the case of a marine ice sheet the ice streams can pull all of the ice from the ice sheet and send it to the ocean as icebergs.
Ice shelves can slow the process of disintegration of the marine-based ice sheet.
Ice shelves form where the the ice sheet begins to float. Ice from the ice sheet spreads across the water surface under its own weight at a rate that increases with the ice thickness. This means that more ice is available as the ice sheet backs across its foredeepened surface and thus, the ice shelf will spread faster . A faster spreading ice shelf has more ice available for calving. Unlike a terrestrial ice sheet, a marine-based ice sheet is susceptible to disintegration by any external factor that increases the calving rate.